Spoilers if you haven't... Well... watched the Arrow.
Slade's anger and rage towards Ollie didn't make sense to me. Besides being angry due to the marikuru making him crazy, he is upset over the death of Shado. Here are my problems with this.
1. He only knew Shado for less than a year if my memory serves correct.
2. They never actually had a thing going.
It would make a lot more sense to me if Shado and Slade's had a relationship instead of Oliver and Shado. It would make even more sense to me if Shado ended up pregnant with Slade's child and he was happy about it. If these developments were to happen, it would make lots of more sense why Slade would want to give Oliver a living hell.
One could argue the following points.
1. Shado loving Oliver would have built anger in Slade for months as they were on the Island due to jealousy.
2. The marikuru is also what added to Slade's obsession with torturing Oliver. It could have fueled his sub-conscious jealousy.
I would like to still argue that these points just aren't believable to me. It would have made more sense if Shado and Slade ended up together on the Island because Slade would have lost someone that he had planned to spend the rest of his life with. Losing that person would be like losing his life also, and dedicating the rest of his time to torturing Oliver would have been a better drive for him.
Other than that, I'm satisfied with the fan service we have received in Arrow, what an incredible show.