What Pokemon can bet Charizard?

Answer 1

Any pokemon that has a type advantage over it, at a reasonable level. For example, if this Charizard is a level 50, if you've got a level 15 pokemon with a type advantage, obviously you aren't going to win. But if you have a level 40-45, and some good moves, you should be fine.

Type advantages over Charizard's type (fire/flying) are types like Water and Electric, which are 2x effective. Rock is 4x as effective, since it affects fire types and flying. Your best bet would be a Rock type pokemon. But, be wary of Ground moves -- they won't affect Charizard, since it's a flying type. Steer clear of types like fighting, bug, steel, fire, and grass. Charizard will mow them down like they're nothing. Any other type I haven't listed is normally effective.