Here is the full list of all 48 Family Guy™: Back to the Multiverse achievements.
Unlock all other Achievements found in the game
Buy everything available in the Store
Earn all 21 stars in challenge mode
Complete all secondary objectives
Complete the "No Place Like Home" level
Play poorly during the final showdown
Acquire any collectible special inventory items and use it 25 times in Story Mode
Earn 10 stars in challenge mode
Complete the "Chicken Fight!" level
Smash your opponent into something 20 times in the "Chicken Fight!" level
Complete the "Chickens In Space" level
Successfully collect $50,000
Complete the "Santa's Sweatshop" level
Kill 500 enemies using Stewie
Kill Vernon
Complete the "Long John Peter" level
Kill 60 enemies with grenades/explosives
Taunt a dead opponent with Quagmire in Multiplayer
Survive 30 waves in Multiverse Madness
Complete the "No Cheese, Please" level
Kill 500 enemies using Brian
Hang around Quagmire in a baby costume for 30 seconds
Perform a multi-kill with a melee weapon
Complete the "Pussy Whipped" level
Perform a multi-kill with a grenade
Survive 15 waves of enemies in Multiverse Madness
Win an Infiltration map
Defeat 10 enemies with a melee weapon
Kill 3 members of the opposing team with a melee attack before you die in Multiplayer
Shut out the other team from scoring in Capture the "Greased-Up Deaf Guy"
Win a Capture the "Greased-Up Deaf Guy" match
Successfully perform a taunt 25 times
Kill Meg during a Multiplayer Match
Win a deathmatch mode (free-for-all or as a team)
Get a 10 kill streak in Deathmatch
Successfully complete your first kill of a member of the opposing team in Multiplayer
Complete the "Handicapable" level
Taunt 5 times in a row with Peter
Select Meg as a character for a Multiplayer match
Kill yourself with a grenade or satchel charge
Complete the "Something's Amish" level
Burn the Amish pot fields
Complete the "It's All Greek To Me" level
Kill 75 enemies with headshots
Destroy all of the piñatas
Switch between Brian and Stewie 10 times in Story mode
Kill an enemy with a single shot to the head
Successfully kill an enemy with one shot