A headshot mode is included in ETPro. It’s controlled by the bitmask cvar b_headshot
0 = disabled
1 = only headshots do damage
2 = instagib headshots : hit = kill
4 = only clients can be damaged, not world entities (e.g. barrels)
8 = you can only receive damage from other clients, you can't receive damage from the world, e.g. from an exploding barrel
The instagib damage is controlled by the cvar b_instagibdamage (default: 400).