What was your greatest mistake ever?

[Deus Ex Machina]

I deleted my uninstaller, and my LF2 is backed up on a disk on key, so no deletion problems.
My biggest mistake therefore (with the magic of Ctrl+Z) was merely a sync problem between my two custom chars (which nobody seems to want to help me fix :/)
(when I add armor to the 3rd standing frame of Deus Ex Machina it crashes SuperHeavy, who has similar armor.)