My Amiibos are hard to kill because of the precise power shielding and dodging, but they are pretty dumb. My Marth often spams side smashes into thin air, usually 4-5 in a row, will only use the first hit of his side-b, does random dolphin slashes out of shield...
Samus on the other hand made a real habit of wasting her fully charged beam by jumping and shooting it off, even if you stand perfectly still.
Both Amiibos seem to not get the idea of punishing, even if they manage to break a shield, they will just jab you or something similar.
I hope I can train them to do more reasonable stuff, and I started with Marth's side-special, but so far I have seen absolutely no progress. :/
When fighting against lvl 9 CPUs, they seem to be vastly superior though. In a 3 stock 1on1 situation they always 2-stock them, mostly because they are almost impossible to consistently hit and 99% immune to edgeguarding.