I want to add one extraordinary case from the Expanded Universe: Lieutenant Erv Lekauf. In a short story A Two-Edged Sword, Lord Vader paid unheard compliments and even showed compassion for him. He valued the Lieutenant's exceptional loyalty, intelligence, and honesty.
"I apologize for our performance, sir," said Lekauf.
Vader noted the use of the word our. "I won't consider that failure in
hand-to-hand combat until I see you fight ordinary men."
"That's very generous of you, sir."
Even the Emperor himself was (at least apparently) positive towards Lekauf.
"Lieutenant," said Palpatine, looking past Vader to where Lekauf stood
in patient silence. "What makes you loyal to Lord Vader?"
Lekauf, normally uncomfortable around Palpatine, relaxed a little.
Vader could feel it. Lekauf's doubts and passions seldom showed on his
face, but he had them, and Vader could always taste them and sometimes
relied on them to understand what was happening within the Imperial
"With your permission, sir," said Lekauf, and looked to Vader. "It's
because my Lord never asks his men to do anything that he wouldn't do
"Laudable," said Palpatine.
In the end of the story Lekauf suffers severe injuries and is taken care of by Vader.
He leaned over Lekauf and stared into his face, seeing a fraction of
the image that Palpatine must once have seen of him. "You are too
loyal for your own good, Lieutenant."
"That's my job, my Lord."
"You never disappoint me," said Vader.
Lord Vader holding an Imperial officer. This you don't see often.