couple of things that tugged at my heart:
Anakin and Obi Wan's exchange of words before obi left for utapau. Knowing that when they met again, it would be under very different terms. And also when obi wan finish chopping anakin's last remaining organic limbs and anakins trying to crawl up to the high ground. And his eyes turn yellow, that tragic music kicks in (The Immolation Scene). Just knowing that anakin went from becoming a great jedi to laying in the dirt with all his arms gone and nothing but his anger. Tragic stuff.