The extreme case of this would be Poison Pills, so if that's allowed then I suspect you can contract for this as well.

Having said that this is the type of thing that is likely to get dragged in front of a judge, so the more foolproof way would be to retain 51% control or dual-class shares. Once you give up majority control to third parties, you can't really prevent everyone else ganging up on you and outvoting you.