lethal friendship

A friendship in where one friend is not in the relationship as much as the other and is willing to put the other's life - work, school, family and friends - at risk in the decisions and choices in that personas friendship.

In How to Train Your Dragon, Toothless and Hiccup have a lethal friendship. When Toothless and Hiccup are first becoming friends Toothless is in danger of hurting Hiccup.