Here is the full list of all 15 Office Battle achievements.
Level all the skills up to 5th level
Reach 55th character's level
Knock 5000 people
Perform ‘To the moon’ 100 times
200 knock-outs in 1 round
Knock 2500 people
Sell 200 items in the shop. Without using "Sell all" button
Buy 100 items in the shop
Perform ‘To the moon’ 50 times
100 knock-outs for 1 round
50 knock-outs in 1 round
Level any skill up to 5th level
Strike critical damage 100 times
Perform ‘To the moon’ 10 times
Knock 100 people