Baldurs Gate 2: throne of baal?

Nope.

Ok then, Diablo 3 seasonal mode is my next guess.

Sorry, not Diablo 3.

Hint: after beating the game, your character becomes the final boss, and the former final boss becomes a playable character.
And it's available on GOG...

Is it a fighting or beat'em up game?

Nope. Although, as in most games, there is some fighting involved.
Hint: 2014

The only thing I can think of that vaguely fits that series of hints is when Putin switched roles with his Premier so he could run for President again in Russia......but I don't suppose anyone made a game out of that, especially in 2014.

Since this thread requires a game guess: Dark Souls 2: Scholar edition.

Rogue Legacy?

Nope.

Nope.
But it has some similarities. The guesses are ascending to a more accurate position. :)

I guess it's a hint... if so then you probably mean Towerfall: Ascension.

Ascendant

You got it!
Really, this game deserves some more recognition... It is a low budget game and has some design flaws (no rebindable keys, no possibility of saving a game, when winning the game can take around two hours...) but it's among the favourites of my collection. Anyway, enough chattering.
You're in charge now :)

And that's exactly why I haven't finished the game. My gaming session are usually below one hour...

Anyway, new one:

What is the easiest way to get somebody arrested? Well put something incriminating in his/her apartment. Like… an apple. No kidding!

Guessing Omikron because there was a insane amount of stuff you could do as the starting character (future MMA cop).