How to stop a command block that is constantly killing me [duplicate]

I was playing minecraft with my brother and his friend. The friend placed command blocks that @kill players infinitely; is there a way to stop this happening? I have tried the commandblockoutput command but it doesn't work.

If you know where the command block is (the coordinate) you can do the command /setblock x y z air. X, Y, and Z are the coordinates of the command block.

If you have access to World Edit, get as close as you can to the command block, and do //sphere [number] water. Replace [number] with the distance (it does not have to be exact) to the command block.

If you don't have access to World Edit, and don't know the coordinate of the command block, you can make a huge area filled with air, by doing the command /fill x y z x y z air. Replace the first X, Y, and Zs with a estimation of where the command block is, and the second ones with an estimation of the command block is in the other direction. Try to make a square with these coordinates, with the command block in the middle.

This is a little out of your way probably, because it takes more work than the reward possibly, but you could download a basic Minecraft server off of the website (Minecraft.net). Place the jar in a folder and run the jar. Accept the eula in the eula.txt when it appears. Then, drag your work from MC to the server folder and open server.properties with notepad. In there, change 'world=' to the name of your world. Run the server and connect (You can just use private ipv4 or ipv6 IP). If all goes well, the server.properties should have disabled command blocks, so it cannot run anymore. If not, go into server.properties and turn off command blocks. When you have broken it, close the server with /stop in the console and drag the world back to Minecraft!

Sorry it is kind of difficult, there is probably a better way!

-Nick