MFR Autospawner with silverfish. Add a grinder for auto kill after a few minutes.
PVP only.
That would easily backfire, quite a bit, and why not just always have the grinder on to kill players?
Trap doors into lava still work the best imho. The simple solutions work the best, because they are least likely to fail/backfire.
Make an entire base, as a decoy, but inside of that base is an obsidian shell containing your real base. Inside of your real base have another obsidian shell containing another decoy. Decoy within the real thing within a decoy. Have nukes set to blow each decoy. If they trip the first decoy without loss, they will enter your real base and realize there is another obsidian shell. Then they might think the real thing is another decoy, so they quickly run inside the second decoy. Unbeknown that there is another set of nukes, ready to go.needs more overkill.
Rig the whole base with a layer of nukes under it and set it to self desturct if someone uninvited invaids