K, this isn't going to be easy but it's annoying me so much.

I'm looking for an anime (I think) movie from the 80's but I can barely remember it. All I can remember is that the protagonist was a pink/white colour (again not poitive) and all I remember that he grows big when he's losing the fights and then wins (obviously). Possibly he had some sort of shiny thing in his chest - maybe his source of power. I used to watch it so much as well and would love to see what it's like now.

I know that not much help but any ideas would be much appreciated

Is it Unico? It's about a little white Unicorn with pink hair. When he needs to fight or help someone in trouble he grows into a big powerful unicorn. Not sure if it's the same thing but let me know.