Well that is not an easy question - there is no perfect one for everyone. Most contain Whey powder, which is dairy, which is a trigger. A lot contain a lot of other junk and sweetners, or artificial sweetners.

Stick to things you know are not triggers- there is egg white protein powder, rice protein powder, pea protein and hemp protein. Then you add it to your own smoothies or whatever, and you don't end up with all the other junk they put in those 'blended' protein powders.

I prefer Hemp protein

Get rice protein, free of dairy and gluten and it is almost same quality of whey.

iso 100 do a protein powder with gluten and lactose removed from it, unfortunately it is around 30 more expensive than most 2.2kg tubs