There are several levels of custom cards.
Weak - Not too challenging to beat, or has such a distinct weakness that finding it to exploit means winning automatically.
Balanced - Not too weak, and not too strong, a pair of balanced cards will yield ultimate fun, espcially when evenly matched.
Strong - A bit too strong for most formats, but can be beatable. Perhaps a strong boss, or a sturdy gimmick.
Broken - Several problematic cards, or some of the same effects that can halt a game, and not make it worth playing anymore.
Busted - This archetype or set of cards needs to thrown in the pit of fire.
Cheater - This player deliberately makes cards that are made to beat everyone, with no weakness whatsoever, and no way to beat that player.
Modern - Your average modern TCG player, which in themselves are beyond a cheater, and not worth considering for skill.
