Here is the full list of all 48 Family Guy: Back to the Multiverse achievements worth 1,000 gamerscore.
You survived 30 waves in Multiverse Madness
You survived 15 waves in Multiverse Madness
You've meleed 3 members of the opposing team in Multiplayer
You have won a Deathmatch mode (free-for-all or as a team)
Your team won an Infiltration map
You used the collectible special inventory items 25 times in Story Mode
You hung around the room with Quagmire in a baby costume for 30 seconds
You killed Meg during a Multiplayer Match
You've successfully completed a taunt 25 times
You taunted 5 times in a row with Peter
You got a 10 kill streak in Deathmatch
You selected Meg as a character for a Multiplayer Match
You've shut out the other team from scoring in Capture the Greased-Up Deaf Guy
Your team won a Capture the "Greased-Up Deaf Guy" match
You completed your first kill of a member of the opposing team in Multiplayer
You smashed your opponent into something 20 times in the "Chicken Fight!" level
You've destroyed all of the piñatas
You burned the Amish pot fields
You killed 500 enemies using Brian
You completed the "No Place Like Home" level
You've been defeated by the T-Rex
You've killed 60 enemies with grenades/explosives
You completed the "Chicken Fight!" level
You completed the "Chickens In Space" level
You completed the "Santa's Sweatshop" level
You've successfully killed Vernon
You completed the "Long John Peter" level
You've successfully collected $50,000
You killed 500 enemies using Stewie
You defeated 10 enemies with a melee weapon
You completed the "No Cheese, Please" level
You completed the "Pussy Whipped" level
You killed yourself with a grenade or satchel charge
You completed the "Handicapable" level
You completed the "Something's Amish" level
You've killed 75 enemies with headshots
You've switched between Brian and Stewie 10 times
You completed the "It's All Greek To Me" level
You successfully performed a multi-kill with a grenade
You successfully performed a multi-kill with a melee weapon
You got your first head shot
You've killed an enemy with one shot
Unlock all other Achievements found in the game
Complete all secondary objectives
Buy everything available in the Store
Taunt a dead opponent with Quagmire in Multiplayer
Earn 10 stars in Challenge mode
Earn 21 stars in Challenge mode