Fish in general. As a kid I absolutely disliked the strong taste and oily texture.
I’m very open with my foods and like to retry everything I disliked in the past, things I still don’t like are Olives (weird metallic taste I don’t like), Tomatoes (slimy texture at normal size, cherry tomats are fine), unaltered boiled egg yolks (so dry, so so dry), Oatmeal (texture issue), and a couple others I can’t think of at the moment. I enjoy most of the texture based ones as soon as the texture is altered.
I’m sure a certain percentage of people can’t spell mastodon.