He's 52% win rate on op.gg right now. His only counters are Singed, Yorick, Swain, Fiora, and Urgot. Swain destroys almost every melee top, Fiora destroys almost every melee top without instant hard CC or mobility, Yorick destroys anyone without sustain and Urgot destroys almost all low armor melees. None of that's surprising. What is surprising is that there are only 9 champions that he has below 50% win rate to while his best matchups have him at 62% win rate and even his "counters" are soft counters at 48-49% win rate except Singed and Yorick.
Play a bursty lane bully? All the damage that would overkill Skaarl is absorbed and it messes up your combos. Then he gets tanky enough to resist your burst and takes you down with his sustained damage.
Play a tank? He has sustained damage and %max HP.
Play DPS? He has some of the highest DPS in the game with his W as well as being able to engage and disengage at will with Q/E.
It seems like there's nothing you can do against him in lane, and even if you win lane, he can just go full tank and still wreck people in teamfights as a Q/R bot.