How do I kill Giant Slimes?
Solution 1:
Solution using commands
If you have access to commands and are playing Minecraft 1.8 (snapshot 14w02a or newer), you can use them to get rid of any mob.
/kill @e[r=50,type=slime]
Kills all slimes in a 50m radius around the player. In the case of slimes, you might have to repeat the command, since I am unsure if it still splits up into smaller slimes. Alternatively
/tp @e[r=50,type=slime] ~ ~-200 ~
teleports all slimes 200 blocks downward into the void, where splitting is no problem.
Solution 2:
Ok, it's solved. We used lava to drown that thing. It's dead now.