Mark Felt, aka Deep Throat
Who pardoned him: Ronald Reagan
What he was pardoned for: His role in the Watergate scandal, namely conspiring to violate election laws
Why it was controversial: Much like the Iran-Contra scandal, the pardons around Watergate were seen as the government knowingly breaking the law, then letting themselves off the hook for it. Though Mark Felt was also Deep Throat, the secret informant who ultimately broke the scandal, this wasn’t known at the time of his pardon.