If an entity is large and powerful enough, is it possible for it to gain a monopoly advantage and manipulate the rises and falls of the virtual currency market?
I think it possible. if that someone has a lot of money to use to manipulate virtual currency market once they sold or bought a huge stock of virtual currency its market will surely change and people will follow with the change. but, it needs big money to do it.
Yes it is possible but i think that it is now becoming difficult, because the use of crytpo currencies is increasing which is also increase the price of crypto currencies, i think that in future it will even become impossible that even big whales will not be able to use to manipulate any single crypto currency.
That is true and in future it will be even impossible to just manipulate the price of it thanks to growing number of users which won't sell their coins with panic and prices will stay more stable for me.