Ben 10 Season 1 - √
Ben 10 Season 2 - √
Ben 10 Season 3 - O
Ben 10 Alien Force Season 1 - X
Ben 10 Alien Force Season 2 - O
Ben 10 Alien Force Season 3 - O
Ben 10 Ultimate Alien Season 1 - O
Ben 10 Ultimate Alien Season 2 - O
Ben 10 Omniverse Story Arc 1 - X
Ben 10 Omniverse Story Arc 2 - O
Ben 10 Omniverse Story Arc 3 - O
Ben 10 Omniverse Story Arc 4 - O

[O = 0-3 Episodes in folder]

Those ^^ are for episodes i did not torrent, you will find all the rest (except from UA S2 and on [i.e. omniverse]) are torrented from:
http://thepiratebay.sx/torrent/7682063/Ben_10_Complete_Seasons_[Ben10_Alien_Force_Ultimate_Alien]_All_E
UA S2:
http://thepiratebay.se/torrent/7504080/Ben_10_Ultimate_Alien_-_Season_2_complete__C_P_

With torrents (Not the UA S2 torrent):
Ben 10 Season 1 - √
Ben 10 Season 2 - √
Ben 10 Season 3 - √
Ben 10 Season 4 - √
Ben 10 Alien Force Season 1 - √
Ben 10 Alien Force Season 2 - √
Ben 10 Alien Force Season 3 - √
Ben 10 Ultimate Alien Season 1 - √
Ben 10 Ultimate Alien Season 2 - None of them - http://en.wikipedia.org/wiki/List_of_Ben_10:_Ultimate_Alien_episodes#Season_2_.282011-2012.29
Ben 10 Omniverse Story Arc 1 - Missing some - max of 10 episodes per arc, see http://en.wikipedia.org/wiki/List_of_Ben_10:_Omniverse_episodes
Ben 10 Omniverse Story Arc 2 - confusing
Ben 10 Omniverse Story Arc 3 - 
Ben 10 Omniverse Story Arc 4 - 
Ben 10 Omniverse Story Arc 5 - 
Ben 10 Omniverse Story Arc 6 - 
Ben 10 Omniverse Story Arc 7 - 
Ben 10 Omniverse Story Arc 8 -