Happiness - he's a cop who's super competent, brave but also just nice. Not immature or cold at all. Also, Happiness is so underrated, it's a great action/thriller kdrama
Doctor Slump - same actor, he's also very likeable here, funny and not mean, although him and the FL have a bit of a cat and mouse thing going on in the beginning but he isn't mean.
Love All Play - he's a golden retriever type of ML, super cute and super dedicated to the FL. I loved this Kdrama, but it gets angsty at times (which i personally love).
Not sure if you only want kdramas, but there's a taiwanese drama which has a cute and funny ML who isn't mean and he's also strong and smart: Someday or One Day