The Great Brain Robbery

How come when a villain enters Flash's body, it becomes unstoppable -- even to his colleagues who would be the ones who are most familiar with his abilities? But when The Flash is himself, he always gets hit, caught, slowed down, etc. in most any situation with the bad guys.

I guess it just followed the typical protocol where the bad guy(s) would always seem unstoppable when the episode starts, but finally seeing The Flash this kick-ass and powerful -- but with someone else controlling his body -- is a bit disappointing, as he rather sucks as himself and seldom reaches his full potential.

If you think about it, he shouldn't really/even be hit with the attacks of anyone whose speed is a million times slower than his (unless they do unavoidably massive, area-of-effect attacks or if he's kind of incapacitated to begin with) ...yet he often ends up getting himself hit somehow, as if every villain also has light speed.

I'm a big fan of the character in general, and this has always boggled me.