One thing i don't get about URF - where characters getting additiona damage?

Some characters like Jarvan should not really benefit from fast ability cd's since his abilitlies not really spammable. But every time i see him - starting from lvl4, sometimes - lvl6 he just goes around and oneshots everyone he sees. No, he does not cast abilities again and again, he simply oneshots. Why? He never did anything like that in normal games. There is no dmg buff in uff. So where do he gets all his damage from?
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