These characters primarily use moves that require charging the stick in one direction and slapping in the opposite direction while attacking. This does not include characters that use moves that they literally charge up (Samus) or characters from a fighting game series (Smash Brothers) which "charge" their attacks by holding a button down.
There is a lot of worry that charge characters cannot be as viable as characters with no limit to move output besides frames. Charge character players require proper execution and timing of moves to win. A fast charge player can throw off Sonic Booms to match most other characters' standard projectiles.