I've always found it difficult to rank music like this since I tend to listen to different music depending on mood. However, there's one song that has stuck with me since I listened through it the first time like 8 years ago: The Great Escape - Seventh Wonder.
It's a 30min song based on the poem Aniara by Harry Martinson and I love it to bits.
If I’ve understood correctly it’s partly scripters/cheaters, partly botting that are the main problems right now, in high and low ranks respectively.
According to some of the discussions I read there’s been a sharp increase in cheating/botting ever since the League source code was leaked.