Hellsing

Once series I've yet to watch, as I don't like dark shows in the horror or gore genre is Hellsing. The series revolves Alucard, a man over 500 years old who is actually Dracula, the strongest vampire (and also a demon) in history. He works for the Hellsing Organization to fight and kill evil forces such as other vampires, as well as the Neo-Nazi group Millennium.

Alucard predominantly wears red, which is representative of blood and fire. he wears a red suit and tie, as well as a fedora that he occasionally wears. His eyes are also red, and he wears white gloves with pentagram seals on them. He has a very arrogant personality, and can be very cocky on account of his near-immortality. He still has the ability to cry despite the fact that monsters like him should have lost the ability to, showing that he still has a human side to him. He also has great respect for opponents that try their hardest in battle and those who die from old age rather than kill themselves, as Alucard is jealous for not having had the opportunity too die from old age himself.

One interesting aspect to Alucard is his relationship with God. Alucard used to be a human (Vlad the Impaler in fact) and fought evil people and did good deeds in God's name. Vlad felt that if he sacrificed enough, God would intervene on his behalf if he were in danger. Vlad was rather extreme in his views and put off a lot of people for his brutality, so much that he didn't have many followers near the end of a war he was currently in. Upon his capture, he discovered that in addition to letting down his people and country, he also lost his wife and child. all because of his desire for power and violence. He felt betrayed by God and subsequently turned his back on him, though he later recognizes that his actions are his own fault and no longer hates God. One of the sources the author referred to in the creation of Hellsing had this same realization by Dracula.

http://hellsing.wikia.com/wiki/Alucard
https://en.wikipedia.org/wiki/Alucard_(Hellsing)

The World God Only Knows (Another Contract)

The World God Only Knows revolves around Katsuragi Keima, a high school boy with an affinity for visual novels and dating sims, having beaten every game in existence and going by the title "Capturing God" online because he can "capture" the heart of any 2D girl. Then a devil from Hell by the name of Elsie tasks him with using his dating skills to recover escaped demons who reside in teenage girls, and can only be removed by romancing them. Keima wants nothing to do with 3D girls though, preferring the idealized 2D versions instead.

However, Keima unknowingly agreed to help Elsie, and as a result now has a collar around his neck that will cut his head off if he does not comply. There is no Satan to enforce such a punishment, as he does not exist in this series' universe. Instead there is the Ministry of Underworld Law Enforcement, which enforces laws and coordinates with the Runaway Spirit Squad HQ, where Elsie is employed with.

https://myanimelist.net/anime/8525/Kami_nomi_zo_Shiru_Sekai
http://kaminomi.wikia.com/wiki/New_Hell