It doesn't matter who you are. Getting your chest cavity caved in by a giant axe hurts.
Things go foggy for a moment. Thanos only distantly hears the syllables he's trying to rasp out using pulverized lungs. "Y--you... should h... hhhhhhh..."
His assailant, the vengeful God of Thunder, says something self-righteous sounding but Thanos doesn't quite register it.
The pain ought to be distracting, but there's only one sensation that really registers in this moment. Not touch, not hearing... not sight or smell or taste either.
The sensation of power. Cosmic. Infinite. Building up at his fingertips.
The brute with the axe grinds his weapon further into the wound. Thanos finds his voice again.
"You." Deep breath. Eyes up. "You Should Have Aimed For The Head."
This is his moment. This culmination justifies everything; every sacrifice and every so-called atrocity.
Everything goes dark as his weary fingers tighten. He fights to stay lucid, to keep his objective framed clearly in his mind's eye. These stones he wields... they are blunt instruments, immense in power but limited in precision--if his focus lapses for a moment, it could all be for naught.
But his focus does not lapse.
Thanos opens his eyes.
He is not where he was. He is not where he expected to be.
Unfamiliar stars shine down upon him from above. Unfamiliar sands crunch beneath his heavy feet, and indifferent waves lap behind him. The scene is dark, apart from the light cast by a lonely lampost outside a nearby coastal village. Its 'bulb'--a glowing rock about two inches across--shades his surrounding in a sickly yellow pallor.
He does not know what planet he's on. He does not know what brought him to it, or why.
He doesn't know much at all about the powers he just unleashed, actually.
All he knows for sure is that, whichever planet he now stands upon, his magnanimous actions have spared it from inevitable ruin.