Minecraft: Xbox 360 Edition

Firstly this must be done in a public match so either grab a friend/booster or a second controller and create a tumble mini game and set it public and snowballs.

Once in the lobby press as soon as possible to ready up and start the match with just you. Have the person going for the achievement stand on the end of the last level of the map but facing inwards then have the person not going for the achievement stand in front of them.

Then the person going for the achievement will spam as they walk backwards off the edge, might be an idea to aim higher too to avoid hitting the block below.

Heres a video of me doing it using 4 controllers, I'm top left (was going for something else at the same time)

Hotshot - 40G (Requires Title Update 48)

Difficulty: Easy

Estimated Period of Time: Short
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To get this Achievement use 2 Controllers by signing your second controller in as a Guest, or else you'll have to get lucky against actual players.

While using a 2nd Controller, as soon as the match starts, purposely throw your Main Controller and 2nd Controller down to the bottom level just above the lava. Have your Main Controller's back to the edge above the lava and your 2nd Controller in front of your Main. As your Main, run backwards off the cliff into the lava and throw a Snowball at 2nd Controller at the last moment while you start falling to get this Achievement.

(Unknown if you HAVE to play this in a Public Match, I personally did a Public Match to be safe and it worked, just make sure you and your 2nd Controller press the X button right away before annoying players join you. Would appreciate confirmation on the Public part)

(Also at the time I'm writing this Achievements are NOT being synced with the site yet, so don't panic if it isn't showing yet)

IMPORTANT NOTE: Thanks to LordFightALot a solution has been found for anyone that was trapped with relocked Achievements on the day of Title Update 48's release! Do as follows and there is a 99% of it working!

"This is exactly what I did:
1. Start up the Xbox (it auto signed in for me)
2. Manually sign out of your profile on the Xbox dashboard.
3. Launch Minecraft.
4. Press Play Game
5. A popup appears and asks you to sign in. Press Yes [I want to sign in].
6. The achievements popped right away on the world selection screen."

If this worked for you, don't thank me, go thank LordFightALot!