Devilman: Tanjou-hen, Shingeki no Kyojin Recommendations
Shingeki no Kyojin pretty much takes the plot of Devilman and adds an Ultraman garnish. In either show, we have an invasion of a hostile race that was once dormant, which is fought by using a hybrid of mankind and the evil race in question. Both include generous amounts of gore, horror, and action. If you want a really high-budget anime with a beautiful artstyle, check out SnK. If you want something with a lower budget but with better writing and execution, watch the Devilman OVAs.