My previous replies were intended to be more tongue in cheek than serious because I am rather passionate about various issues confronting our world and didn't want to start lecturing by going on and on about things that really matter to me... and that can/does happen because some things get me really steamed...
Anyway, and in no particular order because each equally aggravates me...
War.... because of the senseless killing and destruction, pain and suffering it causes.
Child Abusers... because kids are our future and need/deserve better examples.
Politicians.... because they create wars that cause so much death and destruction, pain and suffering... and because politicians are among the absolute worst of child abusers of all, through asinine laws that make parental controls and social boundaries ineffective, thus giving kids the idea they have inalienable rights to things which are/can be harmful to them due to the lack of maturity and life experience.
Organised religion... because most are not, as they claim, doing God's work and must take responsibility/the lion's share for greed, corruption and starting more wars than any other society/organisation on Earth.
There are others, like political correctness and corporate greed, but I'd be here 'til the cows come home... and I don't got any cows.