Am gonna go all out and say mundo, reason being is that:

1) with CDR runes/masteries you'll be throwing those snare-25%hp-cleaver every what? 3 sec? at no mana cost AND the range is ridiculous, so in a 1on1 you can keep everyone away from u while doing amazing damage

2) you have good hp regen, meaning that after the snaring you can slowly recover, all while doing damage

3) his ult is, you guessed it...ANOTHER regen that can recover 50% of his hp

so yeah...those are my reasons...and i honestly think he'll own on a 1on1 empty field no doubt

Hell, just look at a TT tier list.

Tank eve, high damage and high survivability, imagine killing someone and then recovering all your hp? That's insane!

Katarina, no doubt

kat can counter any champions abilities

youre all wrong, its heimer