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 ‘Buy Cheap, Buy Twice', ‘Hide and Seek', 'Ends of the Earth’, and 'Greased Palms’ at C+.
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 a downed suspect only to find out they were faking it.
Arrest your first suspect or civilian
Complete all levels at S.
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 Coyote using only .357 Magnum as a weapon.
Use the secret command for your SWAT team (kill me command)
Be killed by a civilian.
Incapacitate a suspect with a C2 charge.