I think Snorlax would do well, he has some bulk, he could have this moveset:
Body Slam(or any attacking move)
It doesn't really matter but it's always better if it has these things:
if they're roaming legendaries I would go with Wobbuffet or a Pokemon
with Mean Look or Block
it would be best if it has a self-healing move
a move to put the opponent to sleep or any status effect except burn or confused but it's best to make it slee, and that your Pokemon can tank damage.
- Have some good pokeballs like: Ultra Balls, Dusk Balls (if at night), Quick Balls, Master Balls
Hope I helped!