The truth is that most corporations require a two-thirds majority vote and are actually legally bound by some state laws to do so for big decisions (like whether to sell the company). Which makes sense. Is it really a good idea to give your company a self-destruct button that can be activated when almost half the shareholders don't want that at all?
Even if the company doesn't require a two-thirds vote for a decision as big as basically killing itself, there are laws to protect minority shareholders from "oppression" (that's the legal term) by the majority, which kick in during a number of different circumstances, like if the majority owner is doing something that makes no business sense for the corporation and only benefits himself. If the majority tramples these rights, minority owners have the right to sue their pants off.
Also a legal term, referring to suing someone for so much money they can no longer afford pants.
A legitimate case can be made that the owners of the 51 percent in these movies, both villains AND heroes, make some decisions an outsider could consider questionable (Richie Rich spontaneously appoints a team of street urchins as his R&D team), which the minority owners could use to at least start a lawsuit and cause some serious headaches for the "supreme ruler."