Mr Bones is no longer active as a superhero or supervillain, but he’s the director of a division of the DEO (a US government organization in the DCU dealing with magic, aliens, and the like). I’d say that counts as a retirement since he’s mostly behind a desk, or trying to talk active metas into doing his dirty work for him.
Count Vertigo spent some time in a similar position, but, after a run-in with Green Arrow, decided he was wasting himself.
Stripesy (Pat Dugan), the sidekick of the original Star Spangled Kid retired for some time, until his stepdaughter got into his things and decided to become the new SSK. He, for a time was STRIPES, her ‘robotic’ sidekick. Now he’s retired again, acting as a mechanic for the JSA (of which she’s a member - so he’s still able to keep an eye on her).
The JSA’s support staff also includes Ma Hunkel (the original Red Tornado) and Jesse Chambers, formerly Jesse Quick (who’s in a sort of forced retirement as she currently can’t access the Speed Force).
Jesse’s mother, the former Liberty Belle is both alive and retired, last I saw of her.
Wes Dodds (Sandman I) was in retirement when he passed on. Johnny Thunder was sort of retired (he’d gone senile, and couldn’t use the Thunderbolt) when Jakeem got ahold of the Thunderbolt. Whether he’s still retired or dead is a good question, since he was semi-recently merged with the Thunderbolt.
The original Chronos retired for a while, and passed his materials on, but he’s back now.
The original Trickster quit supervillainy and worked with the FBI for a time. He’s apparently back in the game now.
Jack Knight’s already been mentioned, but his father, Ted Knight, the original Starman. was also retired (although de-aged and vital) at the time of his death. (Which I won’t go into details on.)