Dawn of War Wiki

The Great Unclean One is fairly slow, and attacks in melee. His melee attacks aren't super powerful, but they are effective against all targets.

The GUO will almost definitely get killed if he is sent out alone.... He needs to be supported by at the very least heretic worship. Worship heals Him, restores energy (very important, because His abilities are fairly expensive), and gives your commander specific worship buff.

Usually the best tactic for the GUO is to have him break the enemy lines while supported by the rest of your army.

His vomit spit has a fairly long animation and will be dodged almost every time, unless you other units to knock down / disable enemies in the target area. Grenade launcher heretics work well against infantry, as well as blastmaster noise marines. Try to time it right. Otherwise it is good against set up teams.

When using Foul Snare, target squad leaders, heavy weapon operators, commanders, or other priority targets. The snare will not work on units that have force fields up, or vehicles. Once they are snared, focus fire with your army on that target and he will probably die.

Swarm of Flies is an AoE damage and knockdown ability. It will knock down any infantry, including terminators. It also does damage over time and spreads infection to other units.

Use Plague Marines to snare vehicles so the GUO can hit them with melee attacks.

Use the GUO to tank while be gets healed from worship.