I liked Flash for a long time too ( I like characters that have something to do with speed powers a lot ) but he became way too fucking one-dimensional.
To the Endgame part.
Well, not necessarily.
If you realized. Thanos basically won, he literally fucking won. He did what he planned to do and what he had to do more? Act as a ruler he never cared about being? I like the line from the final fight:
This man is literally an embodiment of a victorious villain. Thru Nebula, he realizes that he achieved the victory in another timeline and the opponents he's facing here are leftovers of what is left after his perfect plan comes into fruition.
This man set the plan, put it into motion, and executed it from the beginning to the end.
Our "protagonists" needed to reverse time/go back in time to never allow this to happen so they basically admitted a loss.
Farm Thanos was nothing more than a retired soldier who served his duty as he was obligated to and dipped to live in peace.
The message of the Endgame was massive to me.