I like turtles.
I actually liked Crocomire. Well, not so much the distance as the fact that he was easy to learn. Of course, I haven't even tried shinesparking into him. Apparently you can do that if you kill Kraid and get the Speed Booster before killing Crocomire. But I can't imagine attempting Kraid without High Jump Boots. Confrontation!Kraid is easily the hardest incarnation of the boss (an interesting inversion, since Crocomire and Ridley are actually easier here).