Unreserved apology

[GranToAirMissiles]

What's the difference between an apology and an unreserved apology?

Well, if you're reserved about something, it means there are caveats, concerns, further issues.

So if it's unreserved it means there are none of those.

Not a sausage. But the second sounds more sincere. Since most apologies consist of "I am sorry that you feel that way", they're not apologies at all.