MCU: 10 Marvel Characters Who Will Definitely Die In Phase 3
2. Thanos
Why He Has To Die
There are a few certainties in Marvel movies: jokes, big action set pieces and rubbish female characters all being pretty high up the billing, but the most nailed on assurance you could bet your house on is that the villains die. Unless they're Loki. And since Thanos represents the single biggest threat to the universe so far, there's no way he will be left to lick his wounds after the end of the Infinity Saga. Because, quite frankly, there's no prison that could hold a Mad Titan.
Simply put, Marvel can't afford to not kill Thanos: they've spent a decade building to his threat and to simply allow him to fizzle out quietly would be a disservice to all of that work.
When It'll Happen
At the end of the Infinity Saga - so Avengers 4, by the look of it.
How He'll Die
Unfortunately not by the hand of Squirrel Girl, which would be hilarious. Like Ultron's death, it would be most fitting for Thanos to be defeated by a concentrated team effort by the surviving Avengers, holding hands and singing We Are The World or something.
OR he could be killed off by Nebula after shunning her one too many times...