I am glad I pre-ordered this Endgame version of Thanos as opposed to his Infinity War figure (although that/he looks great) as having seen the movie....
I actually think this Thanos is even MORE of a bad-ass than he was in Infinity War. Yes: he ultimately lost...
BUT
1. He comes to within an INCH of victory despite lacking the knowledge of events that his time-travelling enemies do. AND he doesn't start off with the Power Stone like he does in Infinity War.
2. He adapts to the situation VERY quickly seeing as he manages to discern that time-travel is in effect, who is doing it and why and comes up with a counter-plan where he ALLOWS his enemies to gather the stones for him and then decides to INVADE THE FUTURE to accomplish his goals.
3. He manages to be even MORE brutal in combat, facing far more heroes in a more united front against him - yet he still easily dominates the battle until Steve gets Mjolnir and Scarlet Witch goes full Dark-Pheonix on him. Thanos actually becomes more and more dangerous in the battle as he became more desperate, having seen Endgame I retroactively feel like he held back a little in Infinity War, as if he was just THAT sure in his inevitable victory he never gave any confrontation his 100%.
For me this is Thanos at his most dangerous and therefore the definitive Thanos.