>>149990583
That is the character's whole arc too.
He gets into these convoluted cat and mouse chases with Basil because rats are stereotyped as violent and aggressive, including by Basil himself, and he wants to prove his species is more then that by outwitting the smartest mouse out there and having Basil cause his own demise. That is why he simply doesn't violently kill Basil when Basil is captured like he could, because he does not want the stereotypes evoked. And why when he abandons it and turns violent towards Basil in the end that is a watershed moment.
Also, shows Basil himself is not exactly a great person even if he is in the right in this film, which he is largely doing for his own ego.