Not really.

Let's assume there is one entity with 99% of the hashing power and there are a million entities owning the remaining 1% of the hashing power.
The remaining 1% could always decide to ignore the big 99% entity and fork the chain. The 1% would end up owning 100% of the hashing power again.
Until the 99% entity joins the club again of course.
Now I think of it, could it be possible for the 1% to block the 99% entity?