Fixing up my old cringy comment I made about two years ago, I currently find the Destroyer to be fairly easier as long as you can dodge well. You need to focus on dodging and likely using a Daedalus stormbow with holy arrows, at least in 1.3 (I play mostly on Switch).
Second, I find a tie between Twins and Prime.
Spazmatism in his first phase is innacurate and his second phase, you need to keep distance.
Retinazer, whom I find harder to deal with, is who I go for first. Lazers are high speed and his second phase is ridiculously fast.
Skeletron Prime is hard, but only until you take out the arms. It leaves him defenseless until day arrives, but he can be deadly on Expert if you get caught in his head's range.
I usually fight twins first to get them out of the way and get their loot, since Prime gives you a flamethrower and a Frost moon.
I would say Destroyer is the easiest, Twins are easier based on class, and Prime is the hardest again based on class.