Many ways to counter thorn. Tips like don't repeatedly run out to the sniper lane you just got Thorned from. Try flanking with a grenade ready and don't come around a corner at ground level with your head just ready for him. Talk to the team and tell them his last known location. He will be hunted down and pressured making the bad Thorn users feel frustrated. Played this way and you make the 2 head shots and dot he needs to kill you harder to get. Then you have weapon counters like red death, the last word and I'm sure lot's more. Just my opinion here of course. Edit. Forgot the obvious. If you are all of a sudden green, find cover because you have been Thorned. (a thorn user)