Classic cautionary tale of what genius without morals can bring about.
I found interesting that the same disregard for consequences or others was Griffin's doom itself, going beyond the whole typical "evil does not pay", because it tied to an inability to think long term, see down-sides, and plan. He even admits it himself to Kemp, without understanding the weight or scope of what he is saying, and to Kemps horror too I think. He's a petty sociopath, and he was one before the experiment.
Thomas Marvel, now *snicker*. I love how the simple fellow ended up the winner of the story. Slow but deep thinker indeed.