In Toy Story 3, the strawberry-scented teddy bear who rules Sunnyside Daycare is Lotso, short for Lots-o'-Huggin' Bear. He appears friendly and caring when Woody and the other toys first arrive, presenting himself as a wise leader who can give them a secure new home.
Lotso is actually the main antagonist of the film. He assigns Andy's toys to the toddler room, where they are mistreated, while reserving the older children's room for toys he favors. He runs Sunnyside like a prison, using other toys to enforce his rules and prevent escape.
Lotso's bitterness comes from his history with a girl named Daisy. After being accidentally left behind at a rest stop, he returns home and discovers that Daisy's parents have replaced him with an identical bear. He interprets the replacement as proof that he is disposable and turns against the idea of love and loyalty.
The character's full name is Lots-o'-Huggin' Bear, but Lotso is the standard name used in the film and related references. Big Baby, Ken, and Stretch are separate Sunnyside characters, not alternate names for him.