Here is the full list of all 15 Ready or Not achievements. It takes around 0-1 hour to unlock all of the achievements on Windows.
Complete Coyote using only .357 Magnum as a weapon.
Arrest a downed suspect only to find out they were faking it.
Incapacitate a suspect with a C2 charge.
Be killed by a civilian.
Use the secret command for your SWAT team (kill me command)
Complete all levels at S.
Complete ‘Buy Cheap, Buy Twice', ‘Hide and Seek', 'Ends of the Earth’, and 'Greased Palms’ at C+.
Complete Ready or Not in Ironman mode.
Complete Ready or Not in Ironman mode without losing a single officer.
Complete Port using only a taser, flashbangs, and bash.
Complete ‘Elephant’, ‘Relapse’ and ‘Neon Tomb’ at C+.
Complete ‘Carriers of the Vine’, ‘Sins of the Father’, ‘Ides of March’, and ‘A Lethal Obsession’ at C+.
Complete ‘Thank You, Come Again’, ‘Rust Belt’ and ‘Twisted Nerve’ at C+.
Complete ‘The Spider’, ‘Valley of the Dolls’, ‘Sinuous Trail’, and '23 Megabytes a Second' at C+.
Arrest your first suspect or civilian