This is probably my favorite trophy, but not necessarily for the reasons many would think.
Yes, it's the most challenging difficulty of 3D Dot Game Heroes, where you die in one hit. And you must technically beat the game twice to unlock it. To be honest, I think the FROM difficulty mode was actually harder.
The reason it's my favorite is that it epitomizes how trophies can reward but also entice subsequent playthroughs. I originally beat 3DDGH in 2010, the year of its release and quite enjoyed it. Seven years later, I was watching a video retrospective featuring the game and decided to play FROM mode, and two years after that got the itch to play Spelunker mode. So, it took just over 8 years to get the Platinum trophy.
It's a neat little personal reward for continuing to play the game in different ways, and I think its to the benefit of trophies/achievements when they encourage that type of behavior.