Doomguy has taken down hundreds of demons in the previous games. Taking down hordes that have previously wiped out entire platoons of trained marines with access to weaponry that could have easily teared apart said demons.
Travis has dealt with dozens of people at once, with all of them having weaponry able of hurting him.
He has dealt with stronger opponents before with blows that would have 1 shotted him. Most notably are the Icon of Sin (original), Cyberdemon (with a 10 meter blast per rocket), Spider Mastermind (the leader of hell’s invasion with chaingun fire that would have shredded the marine easily).
Likewise for Travis, he's at an AP disadvantage against most foes, or they have piercing damage that'd kill him with ease, but they're trained assassins with decades of experience and complex powersets he'd initially have no way to counter
Due to the massive hordes of demons he has fought,he has dodged 10’s if not possibly 100’s of projectiles. Especially the hellish levels that were plutonia and tnt.
These projectiles included rockets,fireballs,and bullets.
Revenant’s Rockets: Homing rockets that traced the Doomguy’s place of existing.
Archville Flames: Big walls of flame that also home into the doomguy.
Teleportation: Due to little changes to how Archvilles function within lore,Archvilles in eternal teleport around him. Blocking his shots with a shield strong enough to block the BFG.
Are Plutonia and TNT canon? Huh. Anyway, Travis can deflect machine gun fire and laser beams shot from the eyes with his Beam Katana, and in fact has instinctive reaction so good he can dodge it when it's coming from behind him. There's also spammable blade beams as wide as him, wide bursts of electricity, gunfire from master gunmen, homing rockets, beams as wide as buildings, doves and horny gimps.
Travis also comes from his own society that idolizes and incentivizes training for killing. In his very second fight, he fights the 10th best assassin in the world, with decades of experience, and impresses him so much he goes from dismissive to shocked and encouraging of Travis' pursuit of the #1 spot.
Likely,the crucible has displayed to be one of the most devasting weapons against demon and titans alone. He is seen through artpieces wielding it and in another,using his supershotgun. It is his BFG of the night sentinel age.
Doom Guy got the Crucible soon after he got blessed by the Divinity Machine while the city he is in is invaded by demons, he killed some demons with the sword then sacrificed the sword to take down a Titan.
So the Crucible will likely be the Doom Slayer's main weapon.
I mean, the real issue here is that Travis looks like a moron, would Doomguy really think it necessary to use that on him?
What are Travis skill level/feats, especially against sword users?
He can learn combat techniques in the span of a three-second beating or by reading a wrestling magazine, and he's become the strongest assassin in america (this being a world where assassins are basically celebrities, so there's A LOT of them) by only watching training tapes of a samurai instructor. Early on, he fights the daughter and disciple of this samurai instructor, who's trained for years specifically to beat Travis, and he whoops her ass. Of course, he only gets better and better as the game goes on, receiving something closer to actual training.
Travis' best skill feat, however, is stomping Kimmy Howell,
who could learn in one day what it would take most years to do, and has trained obsessively to beat him. Now, this is the sequel, but while Travis is stronger in this game, this is close to the beginning of NMH2, and Travis did not train between the games, so his NMH1 skill level should be at least comparable to Kimmy Howell, and likely still more skilled.
Keep in mind most of this stuff is done at a huge disadvantage, as his Beam Katana needs to be recharged by shaking it vigorously every 20-ish seconds of combat, but in this match, Travis won't need to worry about that, as NMH1's endgame is the only time in the series you get an item that gives your Beam Katana infinite battery.
Most of his experience is against swordfighters, actually. The #10, #8, #4, #2 and #0 assassins of NMH1 all have swords or something similar, and all are highly experienced in their usage- and don't need to recharge theirs. Travis didn't beat #0, but tied with him, though. Still, a lotta experience.
Another huge advantage he has is Dark Step- if he dodges something at the last second, Travis will get a huge speed amp for 3-4 seconds, and that allows him to chop up anything in front of him. And Travis has Instinctive Reaction, so you bet he'll dodge something.