Here is the full list of all 16 Beat Me! achievements.
Kill 2 players in one round
Kill 3 players in one round
Kill 4 players in one round
Kill 5 players in one round
Win 3 rounds in a row
Win 6 rounds in a row
Win 12 rounds in a row
Win 24 rounds in a row
Kill 25 players in one match
Kill 50 players in one match
Kill a demon
Collect 25 heals in one match
Collect 25 ultimates in one match
Collect 25 Inverse Movement in one match
Collect 25 Anty Gravity in one match
Make triple kill while you are having Absurdly Big Head