I would like to watch anime on legal sites because illegally the risk is too high for me to catch, of course there's netflix crunchyroll but I've already got through it e.g. I want to watch attack on titanium the second and third season but I don't know where are they legally free?
There's not any. Anime on Demand only.
Attack on Titan runs legally on Anime on Demand, but costs a fee.
Other streaming sites: Netzkino, TVNow, Wakanim, Amazon Prime
Wakanim, Crunchyroll or Anime2you (Warning: Anime4you is illegal as far as I know!)