Here is the full list of all 49 Chivalry: Medieval Warfare achievements. It takes around 80-100 hours to unlock all of the achievements on Windows.
Kill 100 Men at Arms.
Have 20 kills with Oil pot
Gather enough experience with spearing weapons
Gather enough experience with light weapons
Gather enough experience with bow weapons
Become a Veteran Man at Arms
Gather enough experience with bastard weapons
Gather enough experience with one handed blunt weapons
Gather enough experience with dagger weapons
Gather enough experience with crossbows
Gather enough experience with two handed axes weapons
Gather enough experience with one handed axe weapons
Gather enough points to reach level 10
Gather enough experience with two handed weapons
Get 10 Headshots with a ranged weapon in one game.
Gather enough experience with one handed sharp weapons
Decapitate 2 opponents with 1 swing
Gather enough points to reach level 5
Shoot 40 arrows into the heart
Become a Veteran Vanguard
Become a Veteran Knight
Become a Veteran Archer
Gather enough experience with polearm weapons
Gather enough experience with javelin weapons
Gather enough experience with two handed sword weapons
Unlock all swords
Play 60 minutes each on Stoneshill, Hillside, Dark Forest and Battlegrounds
Play Chivalry for more than 80 hours
Decapitate an opponent that is on fire.
Gather enough points to reach level 20
Team up with the Mason Order for 20 hours.
Fire 10,000 arrows with the Shortbow
Survive 10 minutes as King in Stoneshill
Successfully block 1000 times
Have 100 kills with the fists
Put out the fire beacon in Hillside
Team up with Agatha Knights for 20 hours.