I know there are dog gods like the Inugami but are there any evil dog gods? By this I mean a god that is clearly evil but still represented as a dog. Cerberus would fit the bil if it where a god and evil. That is the direction I am going for
is a possibility, if you're willing to stretch the meaning of "dog" a bit.
Set is one of the oldest gods in Egyptian mythology. He is usually represented by a mythical sha or "Set-animal" 𓃩 which appears to be some sort of canid in general, combined with some other supernatural characteristics. As time passed, Set himself had an anthropomorphic form with the head of a sha.
One problem with this relates to the "evilness" of Set. Although the Osiris myth where Set murders and mutilates Osiris dates from the 24th Century BCE, Set was also a protector of Ra from the chaos god Apep. Some Pharaohs such as the 19th Dynasty Seti I and II chose Set-based names instead of Horus or Amun-based ones.
Set didn't really become an "evil" deity until the 11th century BCE and onwards.
Traditionally the god of foreigners, Set became associated with foreign oppressors (the Nubians, Assyrians, and Persians) who successively conquered Egypt. This, combined with his murder of Osiris and defeat by Horus, caused him to be regarded as a god of evil. By the Hellenistic age, the Greeks had syncretized him with the monster Typhon.
The closest one (it's not really a god) that comes to my mind is the Norse hellhound Garmr, who is given a mostly evil connotation (he's described as howling and blood-stained, and is associated with the coming of Ragnarok).
Also, in his article The Hellhound, Bruce Lincoln describes a widespread Indo-European motif of two otherworldly dogs: a "white dog of life" and a "black dog of death", of which clearly the latter seems to be characterized as evil, or at least menacing. If you are interested, I recommend you take a look at the article, as he provides many references on otherworldly dogs in Indo-European myth and folklore.