What I dislike the most is:

1) The nerfing of characters powers - Apparently, the writers thought Hiro and Peter had gotten to powerful. So both Hiro and Peter got nerfed in Season 3 by Papa Petrelli stripping their powers. Hiro just got his back to original status afer a season and a half of the writers screwing around with him. Peter's is terrible. Only one power at a time. He's like a watered down version of Rogue from the Xmen. I am still hoping that he will eventually be restored.

2) Misuse of characters powers - Very few of the characters actually have a brain when it comes to using their powers. I have a 5 year old nephew that knows more about strategy and tactics than most of the Heroes cast.

3) Use/No-Use of Claire's Blood - So it was revealed in Season 2 that Claire's blood can bring people back to life. HRG was shot dead and the Company revived him with her blood. So why at the end of Season 3 did they conveniently forget about Claire's blood when Sylar killed Nathan? And then this Season when it is revealed Hiro is dying, Claire offers hers blood but apparently it doesn't work on cancer. So I guess Claire will still need to get mamograms and Sylar should watch his prostate when he hit 40.

4) Really dumb character and plotlines - The latin version of the Wonder Twins from Season 2. Actually, most of Season 2 was stupid as can be. But the blunder twins were indeed the lowlight. Sylar Petrelli or Nathan Gray; second worsed thing in Heroes ever next to the twins. I don't care that a nice side effect was Sylar tomented Matt from within. They could have gotten the same thing from having Matt give Sylar amnesia or some other identity.

In order for this show to really bounce back they need to improve the writing. Season 1 was epic. They need to go back to that quality of writing.