I see he's got one from each actor. But is any Connery Bond film really underrated? The first three were critical and box office smashes, the fourth a box office smash trouncing all future Bonds even when adjusted for inflation (minus Moonraker and Skyfall.) YOLT and DAF always seem to get passes because Connery is in them, and they were box office successes. NSNA might be a better choice for underrated, for while it has problems it's not the outlandish comic book stories YOLT and DAF are.
I'd go with Octopussy for the underrated Moore film. I've always liked LTK but it got bad reviews and lousy box office. QoS maintained box office for Craig, but it's definitely a flawed film. Yet probably the most artsy (each action scene symbolizing the four elements, etc.)
OHMSS definitely qualifies. While TWINE and DAD are kind of messes, the writers rehashed some of their ideas more successfully in future Bonds (Skyfall.) While I haven't seen it yet, it seems SPECTRE has nods to underrated Bonds--OHMSS, LTK, LALD, TB and QoS.