Tetrax, who is the same species as Ben's Diamondhead , was originally a selfish mercenary that only cared for profit. However once he worked for Vilgax he gave him the final thing he needed to destroy Tetrax's home world. After that, Tetrax promised to be an enemy to Vilgax which would eventually lead to him meeting and eventually mentoring Ben Tennyson.
In the rebooted series, Tetrax is the leader of a team of bounty hunters.
Dave's voice is perfect for the deep voiced diamond species and also deliveries a strong no-nonsense performance with hints of warmth. Not surprised why he was one of the few constant actors in the franchise.
I was disappointed that Dave wasn't going to reprise and that, of all people to fill in, Todd was going to fill in his shoes (his diamond shoes? Tyler is right that's hard to do) but I have to say I am impressed. This version of Tetrax isn't the caring mentor and is more a straight up bounty hunter and Todd does an impressive job at that.
Again, I think Todd delivered a good performance that shows some range but I gotta hand this to Dave.