Ruin Explorer
Legend
I dunno if it'll be the obscure subclasses - most of those have pretty straightforwardly bad mechanics, rather than interestingly wacky ones.probably less from 2014 core PHB options and more from stuff like the SCAG Aubclasses nobody talks about anymore that are already funky.
What we don't know is whether 2024 makes significant changes to rules that subclasses might interact with, like grappling (sorry it's the easiest example). If it does, then we'll see a lot more weird issues than if it doesn't.
Also if PHB 2024 Paladins still require a Bonus Action to use Smite I predict we basically won't see any 2024 Paladins lol. Because that's just too much of a power gap.