How we cite our quotes: (Act.Scene.Line)
Quote #7
[…] as we observe in tragedies
That a good actor many times is cursed
For playing a villain's part—I hate thee for't;
And for my sake say, thou hadst done much ill, well. (4.2.278-81)
In a moment that shocks even the jaded Bosola, Ferdinand turns on Bosola after her learns that the Duchess has been executed, per his own orders. He acknowledges that Bosola did exactly what he wanted him to do (done much ill, well), but says that Bosola actually should have defended the Duchess from him, and disobeyed him. Ferdinand has been all about Bosola carrying out his duties to him as minion and spy, but now that the Duchess is finally dead, he tells Bosola that he should have been an "honest man" instead of caring so much about his "duty" to be an intelligencer.
Quote #8
Let me quicken your memory, for I perceive
You are falling into ingratitude. (4.2.282-83)
Bosola flounders as he realizes that Ferdinand is betraying him. He's been thinking that he and Ferdinand are on the same page with this whole intelligencer-prince thing. Bosola is Ferdinand's employee, and the "ingratitude" he speaks of here is the same "ingratitude" he himself feared falling into if he refused Ferdinand's original offer of employment (go check out Morality and Ethics Quote #2 to see that moment in detail). Bosola's been doing all of this terrible stuff because he's been under the impression that Ferdinand will reward his loyalty, only to find out that Ferdinand has absolutely no intention of doing so.
Quote #9
Let me know
Wherefore I should be thus neglected. Sir,
I served your tyranny, and rather strove
To satisfy yourself than all the world;
And though I loathed the evil yet I loved
You, that did counsel it, and rather sought
To appear a true servant than an honest man. (4.2.317-23)
This is the moment where Bosola realizes the whopper of a mistake he's made in pledging his service to Ferdinand. He's known since the very beginning that Ferdinand was a bad guy—he doesn't even like this dude—but devotedly worked as his spy because he thought that Ferdinand would honor the traditional terms of the client-patron relationship and he'd get his in the end. The only way that Bosola was able to justify the fact that he was spying and murdering was to tell himself that he was doing it because he's a "true servant," only to discover in the end that Ferdinand isn't a true master.