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.
Gather enough points to reach level 5
Gather enough experience with polearm weapons
Kill 100 Men at Arms.
Become a Veteran Vanguard
Become a Veteran Knight
Become a Veteran Man at Arms
Become a Veteran Archer
Gather enough experience with crossbows
Gather enough experience with spearing weapons
Gather enough experience with one handed sharp weapons
Gather enough experience with light weapons
Gather enough experience with javelin weapons
Gather enough experience with bow weapons
Gather enough experience with bastard weapons
Gather enough experience with two handed weapons
Gather enough experience with two handed sword weapons
Gather enough experience with two handed axes weapons
Gather enough experience with dagger weapons
Gather enough experience with one handed blunt weapons
Gather enough experience with one handed axe 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
Gather enough points to reach level 10
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
Decapitate 2 opponents with 1 swing
Get 10 Headshots with a ranged weapon in one game.
Have 100 kills with the fists
Put out the fire beacon in Hillside
Have 20 kills with Oil pot
Shoot 40 arrows into the heart
Team up with Agatha Knights for 20 hours.