Is there a nuke command in Minecraft?
Is there a command that destroys everything (trees hills) within a certain radius? I want to create an online world but I always seem to have the spawnpoint in a bunch of trees. Is there like a /nuke command or something of that nature?
No. At least, not in vanilla Minecraft. Sort of. You can use a series of /fill commands to do the job. It's a little limited, but you can do it.
Let's say you want a 100x100(ish) completely flat area. Stand in one spot (the center) and use the following commands:
/fill ~ ~ ~ ~50 ~10 ~50 minecraft:air
/fill ~ ~ ~ ~50 ~10 ~-50 minecraft:air
/fill ~ ~ ~ ~-50 ~10 ~50 minecraft:air
/fill ~ ~ ~ ~-50 ~10 ~-50 minecraft:air
You can also do just one of those, standing on a corner of the desired area, but make sure you have the correct X and Z directions. Also keep in mind that the /fill command can only do 32,768 blocks at a time, so if you want to use just one command, you're going to be very limited in what you can do.
A slightly simpler approach would be to use MCEdit. There, you can just plop the world in a level editor, flatten out your area, and not even need to mess with it. But if you want to do it in-game, that option is out there too.
Or, if starting over is an option, there are plenty of other random seeds out there.
While that is a novel hypothetical solution to starting with a seed you don't like, it is much, much easier to just try again or find a pre-tried seed. Just delete and try again – it is vanishingly unlikely that you will start in a forest every single game in your life.
Regardless, there is no "nuke" command in the list of commands. Even if there was, or you added one with a mod, there isn't one that won't also blow a giant hole in the land that would make the spawn unsuitable for falling/caves/lava reasons.
There are plenty of seeds shared online, and not every world starts you in forest. The last two I tried were Westeros and westeros (yes, I've been reading a bunch of ASoIaF lately) – the former starts you beside a desert village with hills, river, forest, and taiga nearby, and the latter starts you on an island with one tree near some other islands and is excellent for a waterworld survival challenge. Those are evidence that not every seed starts you in the woods.
You can use this execute command:
/execute @e ~ ~ ~ /summon PrimedTnt ~ ~20 ~ {Fuse:60}
Try using the command MULTIPLE times in quick succession. Then there's MASS DESTRUCTION!!!!!!!!!!!!!!!!!!!
Source: MASS DESTRUCTION!!!!!!!!!!!!!!!!!!!!