What is the most powerful fictional planet (from any universe) that Thanos and his army can successfully invade? This means them completely destroying the planet's defences to the point where he can easily massacre half of the population.
Thanos doesn't have any stones and is equipped with his sword and armour. He also gets his entire army from IW/EG, including Sanctuary 2, the Black Order, the Chitauri, Outriders and Sakaarans.
So, what is the most powerful world he can destroy?