Here are a few suggestions and some comments.
1-Radditz-not enough attacks.
2-Nappa-same thing.
3-Zarbon-has a transformation but i can't remember a special attack.
4-Dodoria-not enough attacks
5-Captain ginyu-A good candidate,has plenty of good attacks.The same goes for the rest of the ginyu force.
6-Garlic jr-has transformation and two good attacks.
7-Android 20-Not enough attacks,looks stupid anyway.
8-Android 19-Same thing,and looks like a gipsy.
9-Android 18-Idem.
10-Android 17-Idem.
11-Android 16-Idem.
12-Dabura-has plenty of attacks.
13-pikkon-allthough not a baddy he has nice attacks.
14-Brolly-I know he is a movie character but he has cool attacks and 2 transformations.
15-Coola-I haven't seen him once but i believe he has a transformation and some good attacks.