You'll be amazed, I made a check and if this line had an HasEntProp attached to it, the plugin would be compatible with L4D2:
Code:
SetEntProp(g_iAttacker[client], Prop_Data, "m_iFrags", (GetClientFrags(g_iAttacker[client]) + 1));
I don't know the L4D2 equivalent and I'm too lazy to check but believe me when I say that most L4D2 servers use buy system and the only important thing is that all plugins acknowledged the new killer.
Edit: I don't guarantee it'll work flawlessly with a HasEntProp check but I'm quite sure.
__________________
I am available to make plugins for pay.
Discord: Eyal282#1334