There are plenty of general counters to Olaf, and he pretty much fails as a solo carry past mid gold.
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He needs ult to become a monster, before it activates he can be CCed to death like any other unit, poison comps heavily delays his ult from procing and given that poison is usually comboed with predators or rangers you should have no problem nuking him down.
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Morellos, Super common and top tier item currently, ruins Olaf's sustain if they are dumb enough to still build BT on him, allows damage to stick. Works great on singed, Brand, Senna and many other units that deal AOE. Thornmail in right situation works against him. Though I generally don't recommend drafting chain vests due to the sheer amount of ocean mages and ocean infernos in the current meta.
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Raw burst, a stacked single target burst champ like AP Ezreal or kindred with good placement should have no issues popping him since berzerker jumps can be easily predicted. Each low mana ult should deal around 70%+ of his hp easily, given these 2 units usually have archangels he should die pretty fast.
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AMUMU, pretty much counters everything in the current meta, and works wonders against large groups of melee units for obvious reasons.
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Positioning, If u stack or decide to use primarily melee units with no backline carries ur gonna get rekt. Spread ur units out and his glacial trait will become far less effective. He's not doing damage while he's running across the map.
.... You're also str8 up forcing blender comp which kinda just sucks vs berzerkers str8 up. Jax's dodge + the freeze cc both work wonders against nocturne.