Impressive work by both guys. But... DS would take an all out war by default. He actually has the forces and the experience of waging all out wars, while Thanos is all about stealing artifacts, not waging wars.
I was also surprised at how you mentioned that Apok couldn't roll out and take over Earth, when that has happened 3 times already. Rock of Ages, FC and Batman/Superman. Although you could get a pass for the comment since it's from 07, you probably hadn't known about Rock of Ages at the time.
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Iboga chose not to fight, to allow himself to evolve. He had the wisdom to abandon the actions of war when he knew they would no longer serve him.
Thanos has waged a war before and took over Titan before also. he doesn't need gigantic armies to achieve his means but has been shown fully capable of amassing the means to do so.
Rock of ages is in the future, and in fc he had access to the ale, and was defeated like any threat in the end. When in batman/superman did he take over earth ?