Tinned sweetcorn is a good one to start with, putting some on plain pizza is a good start. Then next time try maybe some finely chopped peppers as well, then maybe some finely sliced white onions before trying red onions which can be more powerful.
Salad doesn't have to be leaf! I like leafy salads, but I also like non leafy stuff like halved cherry tomatoes, diced peppers, and cucumbers with grated carrot with a small amount of olive oil and plenty of salt and fresh ground black pepper.
Cooked veg really does matter how it was cooked when you were tried with it when a kid. Start with the sweeter ones; so carrot, tinned sweetcorn, swede, then leafy greens like cabbage which can be mixed with mash to make colcannon. How you cook them is a personal preference, but I am happy to admit I keep at least 2 bags of the steamfresh bags of veg in the freezer at all times. There's only two of us, so it means less waste and each contain 2/3 different veg. I also tend to use steam bags in the microwave for green beans and then add a knob of butter when dishing up.
It's also ok to say that you don't like something, but keep in mind it takes several tries to get accustomed to the taste of new foods so don't give up within a couple of tries- give it 6/7 attempts, cooked different ways before making your mind up.
I like broccoli, but no way is cauliflower ever going to be a veg I actively choose to eat. If it's dished up at Sunday lunch at my PIL I will make an effort to eat some. But really, I consider it having come from the very depths of food hell.
Plus, despite liking cabbage, kale can get in the sea, and so can cooked spinach although I love it raw in sandwiches/ salads.