OHKO can be stopped by SoA and Damage Reduction, as people above said. Also, you can just pill enough to have 70 attack (unless the enemy has more than 12 pillz or has Hugo).
It's fun to put 2-3 pillz on Kolos (and no fury) when enemy has SoA or DR. He will probably 0 pill it and BAM! You just got 4-8 damage through with so little pillz
Kolos is badass. Very unpredictable. But the fact that people treat him as just OHKO card is a great advantage. Sometimes they forget that they already lost at least 2 life and think that I'm gonna fury my Kolos
To stop Kolos: Plan A DR (safest option), Plan B SOA, Plan C Power = Power.
I once had to use Plan C when Plans A and B are unavailable. When the opponent goes for the KO it's usually 9 pills (and 3 for fury). Use a Power = Power card and put 10 pills on it (there should be 2 pills left) therefore preventing the Kolos KO.
Note: Always works ONLY on Non-Random mode.