Knight

The Knight is the introductory character and and all-around solid character to level. Unfortunately, his Smite ability is glitched and works until the enemy is killed or the dungeon level is exited. This makes the Knight far less enjoyable to play since you only need to level up Smite and HP to survive although the dungeon takes forever unless Smash is leveled and Block (along with Battle Cry) helps keep the initial hits (before Smite procs) low.

The Knight is the third slowest gold farmer in the end game so leveling him up to an end game level is even less appealing.