Oh no! Not the Patagato, Veegato thing again! We were talking about favorites. That's a personal opinion! So let's not have a war over this again! Now on to the point.
Least favorite of the 01 Adventure.
Piedmon- A real asshole, but a good badguy!
Least favorite of the 02 Adventure.
Arukinimon- Evil to the core, but Mummymon loves her.
Kari- Cause she won't make a choise between Davis and TK. She just strings them along!
Least favorite of Tamers.
Yamaki- Turned out OK in the end, but was a real JERK to start off with.
Jeri- Another one who won't make up her mind! She wants to be saved, but refuses the help of Beelzimon when it's offered!
Least favorite of Fronteers.
Tommy- he was a big baby at the begining, but turned out OK later.
Darkmon- *forgot his human name* For letting his dark side rule him and his hatered that leads him to try to destroy his own brother.
SaberGatomon said it, and I'll say it again!