darkSpyro

i noticed when i place on a old character they are very weak compared to a sensei or imaginator is this a bug that was never patched or something?

It's deliberated. It pushes you to play with senseis and imaginators, it's not a bug. But few exceptions, legacy skylanders are way weaker. This has been already discussed in this forum years ago. Just check the stats page and you'll see it perfectly.

Playing with level 20 legacy skylanders in normal mode is like "regular" hard mode in previous games. Playing hard mode with them is not even funny in most cases. Arena challenges, gong challenges and bosses are directly aimed at senseis and imaginators. Without sky-chi or huge stats you're going to sweat to beat them.

Older Skylanders get weaker with every new game installment , but a few of them are still good.
Bone Bash Roller Brawl is really powerful in imaginations

Speaking of older characters getting weaker
Is it me or is Flip Wreck nearly unplayable in Imaginators? He's so weak compared to everyone else. I swear he wasn't this bad in TT. I almost feel like I'm going crazy because I don't remember him being this level of complete dog ass, and I haven't heard anyone else say anything bad about him either

One other thing about another older Skylander, Big Bubble Pop Fizz. For some reason his 3rd "potion" (the acid puddles) don't work properly in the battle arena, which especially sucks for me because that's the main thing I go back to when I replay these games