League of Legends

[Kaden]

edit: apparently the guy is lvl 30, but masteries don't even seem very powerful so I don't know how much of a difference it makes

A level 30 has not only masteries, but access to a full page of tier 3 runes. And on a champion like Jax, who gets tons of benefit from a stat that is very hard to get outside of runes and masteries, it can make a HUGE different.

Of course he could have also been running mana per level and HP5 and a bunch of crap that was irrelevant, but if a level 30 DOESN'T crush level 10s (legitimate level 10s, not smurfs) then he's, literally, the worst player ever.