I say Omastar with its high special attack it can use a whole lot of different special moves. Plus it can learn hydro pump, and even if if Kabutops could, with it's low special attack it really wouldn't do much. Here's my set-up:
Modest +Sp. Att/ -Att
EV's: 252 Special attack/ 252 Special defense/ 4 Defense
Trait: Shell armor
Item: Zoom lens
Ice beam/ Takes care of grass, ground and the overpowered dragon type.
Hydro pump/ +STAB, takes care of your fire problem.
Stealth rock/ Gives Omastar something else to do.
Anything/ I was going to suggest stone edge, but with it's low attack stat and modest nature, it wouldn't do much.
With it's low speed zoom lens gives it +10 accuracy making his hydro pump's accuracy 90 meaning it usually won't miss. With EV's invested in Sp. Defense fire moves will do barely anything with its 1/4 damaged allowing for a safe switch in. Stealth rock will stop sturdy/ focus sash users, also causing some damage.