My successful Platinum Nuzlocke was an emotional rollercoaster. LOTS of deaths, including several unexpected ones during grinding where I just wasn't cautious enough. I got a female Combee somehow, evolved it, but it died, which was pretty devastating. I also hunted for a level 40 Tentacruel for a long time, found it, but it died before it could even level up. Late game I got a Medicham and a Dusclops, but neither of them lived to see level 50. Those were just the deaths I remember from the top of my head, there were many more.
Nevertheless, I managed to get a pretty decent team for the League after all. Torterra survived through the entire game, Bronzong was an amazing tank, Quagsire was surprisingly solid (Swampert-lite) and Togekiss was another choice I wouldn't have made normally but turned out fantastic. With some light support by Raichu (who died against Lucian) and Rapidash (who survived), I managed to beat Cynthia :) Other than Raichu, only Togekiss died in the final battle.