He sure can move. I got 130 kills once with HUNK on that level before dying. That was unbelievable though.

I hardest thing in RE4 mercs is to get started. Leon sucks bigtime so get a new character (anyone is better than Leon). After you get a new character is much more easier:
Ada weapons are great and she is fast. The only boss were she gets in trouble is the Garrador, for the others you can snipe then down. With Hunk you only need a head shot and you will Neckbreak your way to the five stars. And Wesker, well, is Wesker.
Dont know about Krauser though but he has his Plaga arm and a explive bowgun so he cant be bad

^ i agree that leon is just awful in RE4 mercs. his shotgun doesn't even one hit kill most enemies. but the garradors aren't hard to kill with ada. throw and incindieary, and when they are kneeling over, put one round in their back and they are dead. i think krauser kind of sucks. his bows are very inconsistent, and unless you get a head shot there is a lag between the next kill adding towards your combo (if it's a body shot) and it is easy to lose the combo. his best attribute is his arm.