He's battled against oppression for a long time.
He's fought in wars he didn't even know were a thing, not until he became powerful enough to get targeted by the people fighting those wars. And what's worse is that he managed to win the conflicts he had been drawn into, because those people underestimated his intelligence and foresight.
But even with all that experience under his belt, the real enemy he aims for is still far beyond him. Despite how close he gets, his opponent bests him time and time again.
And now he's in an unfamiliar world, home to a familiar-but-not-really species of pretty pastel ponies - and somehow he became one himself. But it's not the new species thing that's the issue, oh no. It's the fact that everyone, everypony, is nice.
Too nice.