Big_Monke
Like the idea and I appreciate that you realize that the Viltrumites needed to be eliminated in order for the Thanos thing to be a threat, but I don't think you played it out right. I mean for one I don't think Thanos' army was ever shown to be quite big enough for the kind of war where he threw endless bodies at them for months on end. Also even if he did I doubt that they where strong enough anyway. His Army in the MCU was pretty underwhelming all things considered. Especially when it came to ground troops (ie only his Children truly stand out and even they weren't all that impressive physically). As such without giving Thanos' ground troops an overhaul/improvement I just don't believe that he could have fought/won a war against the Viltrumites. I'll also point out that if his army did get upgraded enough to deal with the Viltrumites then it would make no sense for them not to be of similar strength when they attack Earth (ie an army of Chitauri in which each individual Chitauri can put up a decent fight against Hulk (or the Iron man armor at least). Honestly I think you might have had more luck if you where just inserted as a Viltrumite.
Read the next chapter. It explains how he took down the Viltrumites. If you had any prior knowledge of how the Viltrumites were originally wiped out in 'Invincible', it should be pretty obvious how Thanos pulled it off with his lackluster army. He used his brain and looked for a weakness. Which, like I said, is explained in the next chapter.
Viltrumite Physiology Superhuman Strength: A Viltrumite's strength is far greater than that of Humans. The upper limit is unknown as some Viltrumites are stronger than others. Superhuman Speed: Viltrumites are capable of moving at speeds much faster than Humans. Superhuman Stamina: Viltrumites generate less fatigue toxins than humans, allowing them to fight and move for extended periods of time without collapsing from exhaustion. Superhuman Endurance: Viltrumites have endurance beyond human capabilities and have survived disembowelment, touching lava, and bomb blasts without permanent physical damage. Flight: Due a complex balancing system located in their inner ears, Viltrumites have the ability to fly. Interstellar Travel: Viltrumites can survive in outer space without aid. Enhanced Lung Capacity: Viltrumites can hold their breath for up to two weeks without breathing. Invulnerability: Viltrumite skin is much harder to pierce than human skin. Only beings of similar strength can harm Viltrumites. Enhanced Healing Factor: Viltrumites can heal from injuries that would normally kill humans. Decelerated Aging: Viltrumites have the potential to live for thousands of years and still be in their physical prime. Dominant Genetics: A Viltrumite's genes will override other race's traits for physical appearance and powers. Viltrumite Weaknesses Vulnerable Ears: When a Viltrumite's equilibrium in their ears is disturbed, mainly by frequency, it can cause extreme pain and may even possibly kill them. Depending on how strong the frequency is determines that pain of attack. Abilities Superhuman strength and able to go Massively Faster than Light. Their enhanced durability makes them almost indestructible and they can only be susceptible to harm by others of their kind or other powerful creatures. Their invulnerability has shown to be as powerful as not at all being affected by the most powerful nukes of the modern day. Average Strength level Average strength is about 100,000 tons but upper limits of some are unknown taken straight form the wiki