Hey Quanchi, i have the best argument in you're Thanos can't die crap.
Here goes.
Darkseid can't die, you do know that right. Hal Jordan after he became the Spectre lobodomizes Darkseid, only for Darkseid to be resurrected.
Guess what Darkseid told him, he claimed he was brought back to life by a power far surpassing that of the Spectre judgment.
So you see, the same argument you use for Thanos can also be use for Darkseid. Does that makes your claim, and my claim true, no. It just proves certain powers don't want them dead. But they can still be killed, even temporarily.