"I will not live as a slave. If you would be free, then fight alongside me."

Drana, Liberator of Malakir

Flying, first strike
Whenever Drana, Liberator of Malakir deals combat damage to a player, put a +1/+1 counter on each attacking creature you control.

The Lost Caverns of Ixalan Commander

Dominaria United Commander

New Capenna Commander

Jumpstart

Battle for Zendikar

Drana's last ability triggers after combat damage has been dealt, so only attacking creatures that survive the combat damage step in which Drana deals combat damage will have +1/+1 counters put on them.

The +1/+1 counter won't change how much damage Drana or any other attacking creature with first strike or double strike deals during that combat damage step. However, the +1/+1 counters that are put on attacking creatures without first strike will affect the damage those creatures deal during the regular combat damage step.