So in terms of fighting intelligence, I don't think it can be called definitively. Zero is undoubtedly the most skilled, but is one of the least tactical and intelligent. X.A.N.A. is the least skilled but most intelligent. Darkrai and Kenobi fall in the middle. I think Sans overall comes in last here though.
In terms of hax
-Kenobi won't be possessed by X.A.N.A. due to his mind manip resistance I think. Kenobi has a flexible power set, as tutaminis allows him to deflect energy, and that'll keep him in the game if he's disarmed, along with telekinesis he can use to make objects into shields or ragdoll people. He has the worst moveset here but also uses it the most creatively IMO, and if might save him if he fights Zero (making him drop his weapon if he's about to lose his head, or using tutaminis to block projectile attacks from anyone here). He can also sense people's alignment in the force.
-Sans could be put to sleep by Darkrai, and Sans can grievously hurt, if not one-shot Darkrai and X.A.N.A. (pretty much pure evil characters) if X.A.N.A. shows him self. He should be able to hurt Zero, albeit less so. He probably can't hurt Kenobi very well though, he's probably the most morally good character in Star Wars. If nothing else, Sans can easily destroy X.A.N.A.'s monsters if X.A.N.A. doesn't go for an avatar for his true form. However, his teleportation and dodging skills means that he'd make the most of his dura. He can also seemingly sense people's morality in the LV system, this will be important later in-character
-Zero doesn't have a universal time stop here, but he has the most versatile hax here between soul manip, mind manip, matter manip, bio manip, intangibility, attack reflection, erasure, absolute zero, status manip, and life drain. However, he has one trump card that makes him quite possibly X.A.N.A.'s worst nightmare for this site. Cyber Elves, which can emulate the Mother Elf. Mother Elf could erase the sigma virus, which was all around the world in many more avatars than X.A.N.A. had replicas, even though the Sigma Virus. X.A.N.A.'s number one priority here is killing Zero, no doubt or question. X.A.N.A also cannot hack Zero because he is immune to casual planetary technopathy.
X.A.N.A., unlike Zero, doesn't have a very useful set of hax in the middle of a fight (EG, he can "just do it"), however, which is ironic because overall he might have the best hax here. However, he's very hard to kill, can summon (seemingly up to a cap though) indefinitely (though it does seem like it takes him time). However, Zero is a pretty bad matchup between no-selling X.A.N.A.'s main power (possession and technopathy). His gravity manip is dangerous, but everyone here has a way to counter it (Zero can survive in space, hook himself to the ground, or just take shelter, Kenobi can TK himself back down similar to Dooku, Sans can teleport, and so can Darkrai. However, I believe X.A.N.A. uses possession the most because it's the most effective ability he has. Since that isn't the case here, he'd go with other moves most likely when he realizes he can't possess anyone (except Sans, but Sans would dodge it)
-Darkrai has a pretty good moveset (in fact second best to X.A.N.A., here IMO, maybe even better than Zero but that's more debatable IMO) but problem is he never really takes full advantage of it like everyone else here does, save for sleep manip and teleportation (to escape Cresselia), and while he can time travel, he doesn't know where it'll take him in PMD so it's a last resort. I also don't recall how he has intangibility. However, his sleep manip is very broken, and his illusion creation would take him far against Sans but wouldn't do much for Zero or X.A.N.A.. It also wouldn't work on Kenobi given his resistance to such things
It's a little inconclusive, but I think hax wise X.A.N.A. > Zero > Darkrai > Sans > Kenobi, at least in terms of applying their hax
Finally, in terms of stamina, it's pretty simple. Zero (Went on after MMZ to fight constantly for an entire year seemingly nonstop) > Kenobi (comparable to Anakin who went through ROTS without food or sleep) > X.A.N.A. (technically limitless, but he seems to run out of juice relatively fast) > Darkrai (was exhausted after a difficult fight (he has the hardest fight in the game besides maybe Wigglytuff), but could still move pretty quick.) > Sans (the least fit here and tired out after a few minutes)
As for how the fight would go, I'm assumming in character.
First off what I think would happen is that Darkrai would get jumped by Obi-Wan and Sans. Both would immediately sense Darkrai's purely evil nature (Maybe X.A.N.A.'s too, but Zero would be fighting him) and would probably try to fight him together.
Second off, Zero might suspect this "X.A.N.A." to be Sigma returned, and would immediately attack all of his monsters and his replicas (cyber elves would inform him of XANA's nature via info manip, so he'd know XANA's weakness pretty soon) to try to destroy every last trace of him
TLDR; this becomes PMD Darkrai vs Sans and Obi-Wan and Zero vs XANA. Because Zero would teleport/transer throughout the planet trying to kill all of XANA's replica supercomputers, the fights might actually break off. This would last for a looooonnnng time, much longer than the other fight, so I'll get to that first.
Darkrai vs Obi-Wan and Sans: Sans isn't going to be one-hit-killed here due to stats equalized, but Darkrai would likely summon pokemon to aid him. This is honestly pretty tricky. Both Sans and Darkrai would be decently matched on their own (hax is not too unbalanced, Darkrai has more stamina, but Sans is a smarter fighter), though I do think Darkrai would take it in a tough fight. But with Kenobi, on his own, Darkrai is probably screwed
However, assuming he tries the same thing he did previously, Darkrai will have weaker, but still helpful minions in Arbok, Magcargo, Aggron, Mismagius, Rhyperior and Magmortor. So, could Kenobi and Sans beat Darkrai plus all of those Pokemon who are at level 36 to his 53?
Honestly, I think so. Kenobi's precog and their shared ability in TK means that if Sans is in trouble, Kenobi might sense it and save him by force pushing an enemy aside, or using a force wave to attack multiple of Darkrai's minions, or throwing them off a ledge or something. Maybe if there's water, throw it at Rhyperior, Magcargo and Magmortar if the force tells him their weaknesses. While Sans likely wouldn't do as well against the Pokemon as Obi-Wan, he would make Darkrai have his hands full since either can one hit the other. Although, Darkrai could try an AOE like Ominous Wind, but Kenobi might reflect it and make him hurt his teammates, or use mind manip to inflict something similar to confusion and Darkrai might mess up and kill his allies. Kenobi's stamina and efficient technique make him an excellent man for a gauntlet. However, the force might tell him if Sans is about to die, so he could use the force to safe Sans either by yanking him out of the way or by misdirecting the attack that would kill him. And if Kenobi fights Darkrai instead, tutaminis will keep Darkrai's sleep projectiles away while Sans can dodge the minions and clean them up pretty quick, since he goes for the kill immediately. However, PMD Darkrai's sleep manip is potentially permanent if there's no resistance, and is very scary (anyone remember Azurill's Nightmare?), and his AOE could hit them both still. And his minions have a pretty versatile power set despite what I'm saying, even though Darkrai is obviously the main threat
TLDR; Kenobi and Sans 6/10. Either party can win but I think
Zero vs X.A.N.A.:: This is nowhere near as close. As previously stated, Zero is probably XANA's worst nightmare. X.A.N.A. can't even kill a few fairly trained teenagers. There's no way he's gonna kill Zero, who even under these conditions would easily solo the Lyoko Warriors. X.A.N.A.'s monsters don't have any chance of killing him at all, XANA's erasure needs him to kill the person first, and while he can mimic Zero's power, he can't just create an army of Zero's with polymorphic spectres. And if his clones have trouble with Ulrich, they don't have a prayer against Zero. He could create a parallel world if this fight took place in Lyoko, but even if he did it's not like that makes much of a difference. He could have an army of monsters inside ala Ghost Channel, but honestly, the results would basically be a repeat Madara vs the Shinobi army. Lastly, posession and intangibility, his best moves for his polymorphic spectre, are both completely useless useless. Zero can damage Cyber Elves, beings of pure energy (The Baby Elves were killed by him), and he is immune to at least planetary technopathy as of MMZ. No amount of Bloks, Crabs, and other monsters is gonna kill Zero. The Kollosus is powerful but can't counter Zero's intangibility. XANA's only hope is to possess Zero, but Zero's ranged attacks and intangibility make that very unlikely. Zero's cyber elves being basically mini mother elves, which erased the Sigma Virus, which is similar in properties to X.A.N.A., means it's just a matter of time, since XANA's minion spam has limits, said minions are nowhere near dangerous enough to take Zero, Zero can kill XANA, Zero won't tire out, and in MMZ transers are basically teleporters (not like in MMX or Classic, think more Instant Transmission)
TLDR; Zero 9/10
After this? Sans and Kenobi are tired, Zero is not. He kills them both if it comes to that. Kenobi lasts longer. Even setting that aside though, even fresh he has good odds of beating them at the same time
However, if they jump him while Zero is destroying XANA I have no idea how Zero vs XANA's minions + tired Sans and Obi-Wan would go. I'll call it even though. Besides, since Zero will be traveling everywhere to kill XANA, they wouldn't even find him
Winner (in character): Zero > Kenobi > Sans > XANA > Darkrai (he'd die faster than XANA)
Bloodlusted and not in character however? It's a battle royale and nobody cares about anything. Zero would likely find out XANA's weakness, once again, but this time it's a battle royale. Kenobi might sense that Zero is the only one who can kill XANA, so he wouldn't attack him. However, Darkrai and Sans have no way to learn this, and I doubt alliances will be made when bloodlusted. So XANA, being the intelligent being it is, would likely make the terrain support Sans and Darkrai, whether by sending minions to attack everyone, or assisting people at points (mainly Sans with Gravity manip). He'd still prioritize killing Zero the second he realizes Zero is a threat to his programming however, so Zero will die first. After that, IDK, but nobody here can kill XANA and nobody here has basically infinite stamina besides XANA and Zero, so XANA will inevitably win because they won't figure out his weakness.
Winner (bloodlusted): XANA > Kenobi/Sans/Darkrai > Zero
Phew, that took a while
