Suicuine

Nope. It’s currently inferior as a water attacker. Just hold onto it just Incase it gets a buff

Vaporeon is superior for now. So no, don't power it up.

Agree with previous: Nope.

Suicune is so far the only legendary without any use whatsoever in the current meta. Others, like Entei and Articuno, have limited use but at least there are use cases for powering them up. Poor Suicune is just too screwed over by Niantic's math. So hold on to it without spending any resources in case something changes.

The hope for Suicune is that, like Gyarados, it will get its moveset changed to include the new Waterfall fast move (and that Waterfall is a good offensive move). With that change, it will not matter what type Hidden Power it has.