>anime protag must fight super bad guy but needs training
>legendary trainer agrees to train them
why doesn't the trainer just fight the bad guy if they're so good???
because trainer used to be the best but he is now old or depressed as fuck, and he is now weaker but he wants to pass his knowledge to main character because he sees potential on him
The only reason he nearly died to the counter attack is because it's THE counter attack to the move. It wouldn't have mattered who did it as long as two people both know how to execute the two attacks correctly the one using the ultimate move/the counter attack will win.
Also sometimes maybe the trainer just doesn't want to fight himself. Maybe he's so powerful he doesn't care, or maybe it isn't his battle.
dude i don't mean to be a dick but i'm fucking huge plus my family is all pro gun southeners, come at me you fat weeaboo piece of shit. it'll be fun using your body as a coach, to sit on.