@Aquasition your opponent had poor late game strategy once you were down to just Arceus Steel. Rather than fishing for the crit with Palkia, he should have sacrificed lugia (simply by switching in, not using recover, and letting burn damage accumulate. If you roar it out to palkia, he switches back to Lugia, if you roar lugia out to skymin, he seed flares) to get skymin a free switch in, then seed flared. That would give him a 68% chance of winning the match (the odds of seed flare both hitting and causing the special defense drop), since Palkia would have broken through by spamming surf. Letting Palkia take the shadow sneak was poor play as well.