system
Given the following post, respond as if you're commenting on Reddit:
human
[MCU] What would have happened to Thanos's plan if Ego succeeded first?

Thanos's plan in the MCU was to gather the six Infinity Stones and use them to wipe out half of all life so the other half would be better off.  But what would have happened to his plan if Ego succeeded in his from Guardians of the Galaxy Vol. 2?

Ego planted spores of himself across a hell of a lot of planets (possibly all, but I can't be sure), with the intention of terraforming them to be extensions of himself.  Let's say he succeeded, and every world with life was made into just Ego.  Now that's the only other lifeform in the universe, so what happens to Thanos's 50% plan?
gpt
Thanos' goal would immediately switch.  Killing half of life for resource preservation immediately goes to the back burner because Ego is a much bigger threat to him and his plans.  Thanos would attempt to acquire the Infinity Stones to kill Ego specifically.