Flying. That's my Cryptonite. It's not necessarily a problem with heights since I do love hiking, but at least I've got solid ground under my feet and if I fall down, well, that's my dumb mistake then for not being careful enough. The mountains and hills are my friends.
Then again I do struggle with sitting on a balcony 3rd floor or higher, I really don't like staircases with gaps between each step and I can not climb up a ladder higher than two meters.
I never fly. Even if you offered me a million Euros, I would not accept the deal. Every time I travel between mainland Europe and the UK or Ireland, I take busses, trains and ferries. It takes fairly long (2 days), it's expensive, but fuck no to flying.
Then again my superpower is to never get seasick. I grew up in a very maritime environment, I knew how to kayak before I learnt how to ride a bicycle at age 5. I love stormy seas, it makes me feel very alive.
Last time I took the ferry from France to England, the ship went into a massive storm. All the furniture was moving around, most passengers got seasick. The lad next to my table was just hugging his table trying not to throw up - while I was sitting next to him with a cold pint of beer, smiling, having the time of my life. :D