Its Mona, because Mona is the closest to a cat and cats are great.

it's futaba!!

Yosuke without a doubt.

Yosuke

y"O"suke

I'd say Aigis, but Koromaru is such a good boy...

For the heroes, I'd say it's a tie between Futaba and Kanji.

For the villains, Adachi without a doubt.

And for the Social Links/Confidants, I'd say it's a three-way tie between Nanako, Sojiro, and Kawakami.