What skill level are we talking about here. Creeper is best at low skill level, spider is best at high skill level. Creeper isnt as versatile and its easily countered but most players at low skill level dont know how to counter creeper. Spider can kill almost any kit easily except wolf and cow. Zombie is capable of the most damage per hit (not including smash crystals) being able to 1 shot the chicken. Though spider takes a lot of practice with the movement and zombie with aim (especially with a high ping).