Toxic has 10 uses in game without item increases 16-18 if you want to use the logic that a trainer will maximize the number of times a pokemon can use a move a part of it being 'well trained', so i'm sure that will do a decent amount of damage regardless of whether you use the @% threshold or the 6% multiplier or even it out to a slower 4% multiplier. And Pikachu is not affected by Electricity if it has lightningrod, because with lightning rod it redirects all electric attacks towards itself, absorbs them, and powers up it's non-physical offense, which would include Grass Knot, hich has been shown to be effective against Water based Pokemon/creatures, and even if you ignore the possibility of Lagiacrus being weak to it because of game mechanics hax, it still does a lot of damage due to LAgiacrus' weight.
A well trained Pikachu would have the same level of intelligence as it's trainer roughly, and a trainer with enough skill to 'well train' a pokemon has plenty of intelligence, and the capability of a Pokemon being able to be 'well trained' by a trainer is only magnified if it's allowed to use it's whole movepool.
And if you count Lagiacrus as an electric/Water type, primarily Electric, it would still be weak to Grass Knot, as Electric doesn't resist grass.
And if Lagiacrus tries to wade Pikachu out in the water, Pikachu can move away from the water and either use Rest to heal itself or use Dig to conceal itself when using Rest. Pikachu also has Secret Power, which when used by the water, lower's the opponent's offensive capabilities by 50%, which would only stack with the 30-48 uses of Reflect and Light Screen to bolster defenses.
If you decide to count Egg Moves, Pikachu has endure, which allows Pikachu to survive any attack with 1 HP up to 10-16 times, Wish which heals 50% of Pikachu's stamina/HP every other turn, Flail and Reversal, which deal much more damage the more damage Pikachu has taken, Tickle which, if Pikachu somehow manages to tickle Lagiacrus (LOL), lowers both offense and defense by 50% along with bide, which allows pikachu to absorb damage for 2 tunrs or 2 minutes roughly, and then retailiate by dealing twice the damage back to the attacker. YOu can also count Signal Beam, which is an attack can can cause confusion and possibly make Lagiacrus damage itself.
Another problem with this matchup is infact GAme Mechanics. In MH, you said there's a 2% continuous poison damage, while Toxic deals 6% on a multiplier, so if you balance them out to be fair to both series, Lagiacrus would take 4% on a slower multiplier. 16 Toxics, even if Lagiacrus takes damage only twice per poisoning and Pikachu has to use multiple toxics every time, equals what, 12% every time it's poisoned with 4-8 seperate poisonings roughly?
It's honestly starting to sound like Lagiacrus has to abuse the limited usages of a Pokemon's move, which, since Pikachu is well trained, Pikachu would pick up on and they'd either come to a stalemate multiple times, or Pikachu would end up winning in an all out battle with neither party fleeing to recover or stall.
But if you can counter everything I've said individually, far be it from me to disagree with Mods chocking this up to a LAgiacrus win, which I'm really having a hard time seeing.
also, on Link being 5-C, i don't see a single problem with that lol. Only issue i have is with all the lolicon magickal girls i've seen being 2-A and higher lol