He reluctantly turned over power and only after he made sure he remained head of the armed forces and senator for life, thus protecting him from prosecution.
You're mistaken. The senator for life thing is a provision in the Chilean constitution that former presidents get - not something exclusive to Pinochet. He remained Commander in Chief of the armed forces for 8 years as part of the plebiscite's transitional provisions, but he voluntarily gave that up too in 1998 just as the terms of the transitional agreement required.