Defaulting to being nice does you no good
But you could try voicing a contrary opinion in a meeting, or occasionally saying no when someone asks you for a favor.
I go out of my way to be a nice guy but I’ve also never been accused of being quiet or of not voicing my opinion. Being nice doesn’t always mean being quiet. In fact, in some ways it is nicer to let people know how you feel rather than keeping it to yourself.