First of all how do you qualify a whale trader? Example a trader holds 200btc is it whale? I think no, so if this guy for ex. Dump coins it will not affect the price but if a person roger ver holder of 300,000 btc and will support bitcoin unlimited the split coin ( if there will be split coin after hardfork on august 1) then he will dump all of his btc and will support btu, itll surely affect the price,
So to deal with kind of acenario is to be prepared by reading reviews, speculation and forecast and out of it will be the basis of your dexisions
it depends on what market you are talking about! in bitcoin there are many whales and market is huge, so you really can't be considered a whale no matter how much bitcoin you have because if the market and other whales are against you, you won't matter.
in altcoins there are two kinds. the manipulated ones and small ones. the manipulated ones like ethereum have a lot of money in a centralized group behind it. they have the foundation and a lot of funds to control the market. nobody can put a dent in it.
in a small coin sometimes it is even possible to become a whale with 1
BTC! and yes i have tried and it is possible