Most fun for me to design was either Thrull or Yuras, which both have their reasons
Thrulls reason was mainly because unlike Tronus, Thrull was someone i actually invisioned a designed for and didnt just go off the bat with no thought.
For Yuras, hes just so simple in design, yet its perfect for him. Ive taken inspriation from Bibically Accurate Angels for his design, which just makes it fun for me to do it every time.
In terms of story telling, its probably Tronus, and second would be Boltamus. (dw tho about Infernal, hes gonna get his spotlight soon enough)
Tronus ive always tried to paint as this battle scarred warrior who does have good intentions, but does them in a cruel way, as he wanted to do his plan no matter the cost
And for Boltamus, i just LOVE the charater arc he had, at first he was a asshole but now hes reformed and a actually good charater