I've found that putting multiple nukes nearby each other and setting them off makes for some pretty big explosions under MindCrack. As in, giant, potentially server-crashing explosions that likely approach about a hundred blocks in radius and take out everything except the bedrock. A single nuke, by comparison, maybe has a radius of about 50 blocks and probably won't dig very far into the ground at all.
After firing off a few of those in creative I learned to encase a chunk loader in bedrock at the middle first, because many, many blocks survived as item entities and hence needed to remain chunk-loaded for at least five minutes before they despawned. Actually sitting myself anywhere near the area during that time reduced my frame rate measurement to 0.