You may be looking for the Sonic Adventure enemy, E-06 Bladed Spinner (Spina).

Spina (スピナ, Supina^?) is one of Eggman's robots from the game Sonic Advance 2. It is a purple bat-shaped robot that attacks enemies by spinning bladed wings. It is similar to the E-06 Bladed Spinner robot from Sonic Adventure, except that it is purple instead of blue. It reappears in Sonic Advance 3.

It cannot be hit from the sides because of the shield of its wings, but a strike to the head can destroy it.

Spinas also appear as enemies in Sonic Colors.