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