Thanos knew that he was out-matched against Tyrant. Thanos was testing the limits of his durability for future plans, he knew that he couldn't keep up in a sustained fight against Tyrant. Death enhanced Thanos to an unknown degree when she brought him back, and Thanos was testing the limits of what he could take for unknown future missions and calculations.
Thanos got his mission accomplished, so he left. He got exactly what he wanted. Had the fight continued, Tyrant would have won. There were some signs that Thanos possibly sustained internal injuries in his fight both against Odin and Tyrant, and was healing himself internally as he got back up. That being said, it was still a very impressive feat for Thanos to survive that attack.
Oh and this match is chump change for Tyrant, btw.
First off, I agree that Thanos would have been killed in his battle with Tyrant if the battle had continued. No question about it. However, battling him to the death wasn't Thanos' objective. It was to steal a power orb and withstand Tyrant's assault. He proved he could so chose not to continue.
In regards to the orb, is everyone forgetting that when Tyrant sent Morg after Thanos & co, he gave the Power Cosmic back to Morg? Tyrant said (paraphrasing) "As reluctant as I am to do so, I will reinvigorate you with your Power Cosmic." So, exactly how much power was in the orb that Thanos had, we don't know.
As for the fight in question, Tyrant wins 10/10.