Original Half Life/Half Life: Alyx/Unused enemies

Civil Protection/CP Police

Combine Grunt

Combine Soldier 

Combine Shotgunner

Combine Elite/Overwatch Elite

Combine Charger

Combine Suppressor

Combine Sniper

Stalker

Strider

Hunter-Chopper

Gunship

Dropship

Mortar Synth

Crab Synth

Hunter Synth/Hunter

City Scanner/Scanner

Shield Scanner

Combine APC

Manhack

Rollermine

Cremator

Assault Synth

Synth Guard

Combine Assassin

Combine Alien assassin

Combine Super Soldier

Combine Heavy Guard

Others

Combine Heavy Tank

Combine Riot Tank

Combine Darkwalker Synth

Combine MBT

Strider tank

Eel Synth

Tank Synth

Lancer Synth

Starblaster synth

Combine Interceptor

Combine bomber fighter