User blog comment:AdmiralPedro1stFleet/FANS PLEASE READ. Drew Karpyshyn's ORIGINALLY INTENDED ENDING/@comment-1440333-20130525133723/@comment-1786741-20130525175434

Destroy is essentially an advanced EMP and control is just a singal that overwrites/changes the Reapers. Synthesis changes the DNA or organics to be partly synthetic, that's a PRETTY big step compared to the other 2. The first two are somewhat believable and wouldn't be too hard the explain.