Cave Story 3D. It just felt like the worst version of the game, the 3D effects made me feel sick to my stomach (this is the only time 3D effects have done this to me, so it's not just a general issue with 3D), and there were parts where it was literally impossible to see where I was jumping to due to a piece of the foreground. Aside from that, though, there's no games that have hugely disappointed me for 3DS, just some that were only just worth the money. --- It's better to be a smart ass than a dumb ass; if you have nothing nice to say then say it often and loudly.
Can't imagine regretting overclocked or tales of the abyss. I do regret buying cartoon network punch time explosion. Hey, c'mon, it was like 12 dollars and i had leftover store credit from paying for Fire Emblem Awakening.
Kingdom Hearts. First game I bought. I bought Samurai Warriors for $13 a week ago, and I've had more fun in a repetitive game like Samurai Warriors than I have in Kingdom Hearts. And this is coming from someone who loved the initial KH games and is a huge RPG fan.
I'm easy to please, but KH:DDD just felt...stale and pointless to me. I tried, but I couldn't get into it.