aggressive, forceful
very effective
(also kick-butt or kick-yer-ass) Rough; powerful; rough-ass, tough: that kick-ass attitude/ gave up its last drop of kick-ass Gewurztraminer/ the only team without a kick-butt run blocker on their line
nounPower; energy; virility: He's the guy who coaxed the kick-ass back into the torque/ with the gall to label such Muzak kick-ass (1970s+ Army)