Zuko, The Banished Prince, The Traitor Prince, the Avatar's fire bending teacher and the 37th Fire Lord had ruled for 46 years before retiring and passing the throne to his daughter. He had sailed from one end of the world to the other, crossed continents, and seen legendary creatures and spirits. Zuko had survived countless assassination attempts on his person, the first when he was ten years old by his own grandfather, to the numerous he'd thwarted after taking the throne. He had quelled a civil war in his country before it started and helped reunite a world of people after a hundred year war.
Zuko had many regrets - he'd made more mistakes than he could remember. But even so, he was happy with the way his life had turned out. His mistakes made him who he was, and if given the choice, he wouldn't change any of it. Well… maybe he would make a couple of changes. Some of the things he did were monumentally stupid.
But that aside, Zuko was content as he lay in his bed, feeling his inner fire slowly fade. He was at peace with himself and was looking forward to seeing old friends and his uncle in the spirit world. And so, surrounded by his children and grandchildren, Fire Lord Zuko passed away.
But the end is never really the end. Time keeps ticking and life continues on. For Zuko, the universe wasn't ready to let him go so easily. He and Sokka had an on-going competition for the title 'most hated by the universe' - they never did agree in the end.
And so the first feeling Zuko had when he was reborn into the time of the bloodiest war in shinobi history as the heir of a ninja clan was vindication.
He always knew he was the universe's favourite punching bag.