Name times where a character was...

...disappointed by the motive of another: tvtropes.org/pmwiki/pmwiki.php…

Listed:
"Clank: There must be another way to make a home for your people!
Chairman Drek: You think that's what this is about? Who do you think polluted our last world? I did! This is about one thing and one thing only: cash, and lots of it. See, I've been paid for every square inch of my new world. Once the new inhabitants move in, I'll begin polluting this world as well, and the whole thing starts all over again. Ah... brilliant.
Clank: Why, you... you evil little...
—Ratchet & Clank (2002)"

"Sly: So, before we finish this, let me get one thing straight: you came after the Coopers because of what happened to your father?
Le Paradox: No, you imbecile! I came after the Coopers to prove that Le Paradox is the greatest thief who has ever lived! Is there any doubt? Ask yourself this: if the Coopers were truly the greatest thieves in history, and I have stolen their most valued possessions, then what does that make me?
Sly: Ummm... an idiot? You had it made! You could have been the biggest thief of all time, but you had to target my ancestors and blow your own cover. You exposed your operation because of your ego! No Cooper would've done that. And for the record, can you really say you stole the canes? Seems like your "friends" did all the real work.
—Sly Cooper: Thieves In Time"

"In Phineas and Ferb The Movie: Across the 2nd Dimension, Alternate!Doof's tragic back story is that he lost a toy train as a child. Immediately lampshaded by Prime!Doof who lists off tragic back story after tragic back story."

In Castlevania(64) and its Legacy of Darkness remaster, Actrise tells kid hero Carrie Fernandez, right before their fight, about the time she(Actrise) slew her own child in attempt to gain immortality, Carrie quickly calls it pathetic in contrast to her(Carrie's) stepmother making a sacrifice to save her stepchild's life.

Edward attacked Shou upon realizing that the talking chimera from two years ago was his wife and that the new one was his dog and child.
As you should know, Shou did that crud in an attempt to remain a state alchemist, what's more is that he not only expected what he did to his family to be acceptable, but also expected it to be rewarding.
He was scheduled to be stripped of his certification and court martialed, but that never happened due to the state alchemist killer called Scar getting to Tucker first.
•This might be a meta example as Shou's motive for his actions disappointed everyone in real life too(Including the author).

In Metal Gear Solid V: The Phantom Pain, Venom Snake and his buddies find out that Huey Emmerich murdered Dr. Strangelove, the reason: she was against their son, Hal, being a test subject in his mad experiments.
Needless to say, many people who knew(including both the characters and everyone in real life) were outraged by this.