Blondie was "The Good" In Name Only throughout the entire film, considering he was just as greedy, selfish and heartless as Tuco and Angel-Eyes. However, towards the end of the film, he finally lives up to his namesake as he comforts a dying soldier with One Last Smoke from his cigar and give him his jacket to keep him warm in his final moments, in an act of spontaneous and selfless kindness that seemed so-alien to the grim and cynical world of this film.
In the extended cut, after offering liquor to a Confederate soldier for information about Bill Carson, Angel Eyes lets him keep the entire bottle. For a cold-hearted person, that's pretty generous of him. Upon seeing the wounded and dying soldiers in the fort, he also appears to be quite moved and shakes his head sadly.
Another touching moment is between Tuco and Blondie after the fight between Tuco and his brother. Tuco doesn't know that Blondie saw the fight, and tries to convince Blondie, if not himself, that his brother loves him and looks up to him, and we see the underlying sadness in how lonely he is and how his only "brother" is Blondie. Made much more sad when one thinks of the ending.
One of the best parts is Blondie's "and after a good meal, there's nothing like a cigar". He may be cold and pragmatic throughout most of the movie, but this little gesture of friendship and willingness to play along with Tuco's lie shows that he feels compassion for him, at least a little.
Not immediately obvious, but the final scene. Sure, Blondie leaves Tuco tied up, almost kills him and leaves without as much as a word. But think about it - he lets Tuco leave, lets him keep the gold, and indirectly tells him (by shooting the rope) that their score is settled. For a tough gunslinger, that's as close to explicitly making peace with Tuco as it possibly could be. (Also let's face it: It's Tuco. The best way to make peace with him is with a good running start, just in case)
The scene where Blondie pets a Cute Kitten sitting in his hat.
The Captain's (forget his name) expression when he sees the bridge blowing up and is finally able to die in peace.