Here is the full list of all 18 Oh...Sir!! The Insult Simulator achievements.
Play more than 100 duels.
Unlock a secret character.
Compose a phrase with "Your mother is your father".
Take 50 honour points off your opponent in a single insult.
Compose a phrase with "Your country is not a part of Europe".
Complete the Insulting Tournament.
Unlock two additional characters.
Win your first argument.
Play the basic tutorial.
Compose a phrase with "A duck hunter probably murdered this poor man".
Compose a phrase with "Your beloved auntie worked with the Nazis".
Compose a phrase with "Your mother was a hamster".
Compose a phrase with "Your hovercraft is full of eels".
Compose a phrase with "You still use Windows Vista and never watched Star Wars".
Compose a phrase with "You are silly, and everybody knows that!".
Compose a phrase with "Your wife is interested in photography, nudge nudge!".
Compose a phrase with "Your son died because of your sins!".
Mention Satan 66 times.