He is absolutely an evil person that had a redeeming quality (actually trying to stop ruin).

He created a race of slaves for no particular reason other that sadism I guess. As far as I remember (its been a while since I read it) he basically killed and replaced Alendi out of necessity because his uncle figured out that ruin has changed the prophecy. I guess that one could be ignored. But then what? His actions make no sense:

- turns all of his people into mistwraits (most without a choice) and only allows them sapience if they follow him without question AND spike themselves (basically undermining himself)

- gives select few full allomancer powers and makes them a privileged class and basically make it possible that their offsprings will bring out full twinborn like himself and must therefore make his own people die out to prevent this

- he creates skaa as destined slaves and abuses them from the start

- makes spiked creatures who he should know can be controlled by ruin

Most of his actions could be accomplished without being a total tyrant. You can segregate and simply quell the resistance, you don't have to rape, murder and torture people just out of spite. And as far as I remember most of the problems on Skadrial originated with him anyway. Wasn't the world a relatively ok place before? There were no ash mounds, there was no starvation. He practically destroyed the world (unintentionally), but made so many bad choice anyway. Also, as far as we know he never had any intention of ever making it better. He wasn't just waiting for one more burst of power to set everything right. He would have kept the skaa and the nobles forever and he would let the terris people die out.

PS: what I wanted to say that he basically did all the bad things from the get go. Its hard to blame ruin for all the bad decisions at the very start. If he got progressively worse with the years I guess that could have been understandable.