Octavian Grant is a human Grand Admiral and Tapani noble, one of the twelve appointed in 2 BBY, and a Star Wars Legends character developed further in "Who's Who: Imperial Grand Admirals", Star Wars Insider 66 (2003). He was a genuinely capable tactician in the Clone Wars, an open humanocentric who despised non-humans — Thrawn included — and entirely uninterested in Imperial court politics.
After Endor he did the one thing none of his colleagues thought of: nothing. He waited inside Ardus Kaine's Pentastar Alignment while the other Grand Admirals declared themselves emperor, flew into stars and rammed each other, then defected to the New Republic two years later, trading Imperial military secrets for immunity and a retirement on Rathalay. He later helped the Republic against Kaine — engineering the ambush that killed him — and finished as the last surviving Grand Admiral, living out his days under New Republic surveillance.
Catalogue entry. This figure has a verified record here rather than a full write-up — the encyclopedia labels its own depth instead of padding it.