Not always, no. Otherwise we wouldn’t see successful murders, genocides, acts of vengeance, acts of cruelty, deliberate rises to fame or accumulation of power, emotional manipulation, public shaming, all that stuff. All of that can be very successful. Even getting married can often times be said to be a success of the ego.

It doesn’t really have an opposite effect on the ego, no. In fact, it usually has a positive, soothing effect on it - that is, it gets what it wants and is happy for a while. The problem is, it never makes it happy in the long term. Whatever was achieved or done does not bring lasting happiness, and sooner or later, it gets disillusioned in its achievement and needs to do something else, find another goal, another source of satisfaction in its constant quest for happiness and fulfillment.

Does it often times have the opposite effect on other people? Sure! A good example would be the war on drugs or our society’s rehabilitation system (prisons). It usually has the exact opposite effect on people who go through it from what it was intended to have. But ego doesn’t really consider other people as independent free individuals or knows them all that well because it doesn’t know itself - so it usually thinks that it knows better what other people want, need or how they should be and behave. Most of the time, it means “they should all be like me or bow to me, because in my personal hierarchy of values I am surely at the top”.

That’s the defining characteristic of the ego, not the amount of influence or power one has, necessarily. Warren Buffet has probably a much smaller ego than a typical young bride.