Why Grimmel and Viggo are such good villains

After reaching RTTE for like the tenth time (never seems to get old), it occurred to me how similar Viggo and Grimmel really are. And how good of villains they are as well.

They are both dragon hunters, both devious, both love "playing with their prey". They're the only 2 who have realistically been able to mess Hiccup really bad. Sure Drago temporarily stole toothless and killed Stoick, the red death took hiccups leg and almost killed him, Daggur attempted to wipe berk out completely, Krogan was the first to face hiccup with his own dragon riders etc. But Hiccup could predict the next move of these guys.

But it was Grimmel and Viggo who were really able to get into Hiccups head and play games with him like he was their toy. Hiccup for a long time never knew what Viggo or Grimmel's next movies were going to be.

But what really interests me between them is the contrast. Grimmel is a killer. He prefers to do the hunt himself. Viggo is a business man. If it wasn't for Hiccup possessing the dragon eye, Viggo wouldn't care about Hiccup in the first place.

Viggo considered Hiccup a foe, but he never really cared for killing him because Hiccups life doesn't matter to him.

Grimmel on the other hand sought out Hiccup. He could not standby while he, the nightfury killer let a nightfury live.