Did anybody ever try to talk sense into Voldemort?

Question

We get it. Voldemort is the Hitler of the wizarding world. He's filled with racist thoughts, supremacist ideas, etc, etc.

But while these ideas probably came to him very quickly, as he was fascinated by "good ol' Slytherin clichés", he spent several years in a school, and schools are supposed to notice this kind of patterns. Even outside of school, there were probably a couple of other persons who witnessed the "orphan boy raised by Muggles" tending to psychopath ways, until the point where it became evident (Wizarding wars and all that kind of things...).

Granted, he was a bit secretive about it when he was still a student (see following quote), but you would expect Hogwarts staff to have some cunning teachers to spot the behaviour.

I AM LORD VOLDEMORT

“You see?” he whispered. “It was a name I was already using at Hogwarts, to my most intimate friends only, of course."

_{Chamber of Secrets, Chapter 17 - The Heir of Slytherin}

Dumbledore definitely knew by the time Tom Riddle came for the DADA position, but he did not seem to try and do anything to talk sense into him:

“So, Tom… to what do I owe the pleasure?”

Voldemort did not answer at once, but merely sipped his wine.

“They do not call me ‘Tom’ anymore,” he said. “These days, I am known as —”

“I know what you are known as,” said Dumbledore, smiling, pleasantly. “But to me, I’m afraid, you will always be Tom Riddle. It is one of the irritating things about old teachers. I am afraid that they never quite forget their charges’ youthful beginnings.”

_{Half-Blood Prince, Chapter 20 - Lord Voldemort's Request}

But out of all the wizards, there must be at least one naïve enough to try and get him to change his mind¹. So, is there any evidence of anyone trying to have an helpful dialogue with Tom Riddle/Voldemort about his debatable conceptions of the world? ²

---

¹ Even if I fully realize telling the Dark Lord "let's sit down, have a cup of tea and talk about this, okay?" is borderline suicidal.

² "Please don't kill me" and the like when Voldemort's about to Avada-Kedavra you don't count, of course.

Answer 1

Dumbledore did when introducing him to the wizarding world.

When Dumbledore told Tom Riddle he was a wizard, he also talked to him about how stealing isn’t allowed at Hogwarts, and how he must abide by wizarding law or suffer the punishment.

“You will return them to their owners with your apologies,’ said Dumbledore calmly, putting his wand back into his jacket. ‘I shall know whether it has been done. And be warned: thieving is not tolerated at Hogwarts.’

Riddle did not look remotely abashed; he was still staring coldly and appraisingly at Dumbledore. At last he said in a colourless voice, ‘Yes, sir.’

‘At Hogwarts,’ Dumbledore went on, ‘we teach you not only to use magic, but to control it. You have – inadvertently, I am sure – been using your powers in a way that is neither taught nor tolerated at our school. You are not the first, nor will you be the last, to allow your magic to run away with you. But you should know that Hogwarts can expel students, and the Ministry of Magic – yes, there is a Ministry – will punish lawbreakers still more severely.”
_{^{- Harry Potter and the Half-Blood Prince, Chapter 13 (The Secret Riddle)}}

We don’t know if Dumbledore tried to talk to him more than once, or any time after this first meeting, but we do know that after that, Dumbledore decided to keep a close eye on him.

“Let us say that I did not take it for granted that he was trustworthy,’ said Dumbledore. ‘I had, as I have already indicated, resolved to keep a close eye upon him, and so I did. I cannot pretend that I gleaned a great deal from my observations at first. He was very guarded with me; he felt, I am sure, that in the thrill of discovering his true identity he had told me a little too much.”
_{^{- Harry Potter and the Half-Blood Prince, Chapter 17 (A Sluggish Memory)}}

Tom referred to ‘the old argument’ about love being more powerful, which, though it could be about Dumbledore’s general views, could also be about arguments Dumbledore made to him specifically.

“Of some kinds of magic,’ Dumbledore corrected him quietly. ‘Of some. Of others, you remain … forgive me … woefully ignorant.’

For the first time, Voldemort smiled. It was a taut leer, an evil thing, more threatening than a look of rage. ‘The old argument,’ he said softly. ‘But nothing I have seen in the world has supported your famous pronouncements that love is more powerful than my kind of magic, Dumbledore.”
_{^{- Harry Potter and the Half-Blood Prince, Chapter 20 (Lord Voldemort’s Request)}}

By the time he asked Dumbledore for the Defense Against the Dark Arts teaching post, though, we know Dumbledore had already given up hope of trying to talk to him.

“Then we have nothing more to say to each other.’

‘No, nothing,’ said Dumbledore, and a great sadness filled his face. ‘The time is long gone when I could frighten you with a burning wardrobe and force you to make repayment for your crimes. But I wish I could, Tom … I wish I could …”
_{^{- Harry Potter and the Half-Blood Prince, Chapter 20 (Lord Voldemort’s Request)}}

It’s unclear how many times Dumbledore tried to talk to him about what he was doing, but he did at least once, and he monitored him very closely after that day.

It’s also possible that Mrs. Cole at the orphanage did.

Tom Riddle was very suspicious of Mrs. Cole - when Dumbledore came to tell him he was a wizard, he thought that she’d called the asylum to report him as mad or have him looked at.

““Professor”?’ repeated Riddle. He looked wary. ‘Is that like “doctor”? What are you here for? Did she get you in to have a look at me?’ He was pointing at the door through which Mrs Cole had just left.

‘No, no,’ said Dumbledore, smiling.

‘I don’t believe you,’ said Riddle. ‘She wants me looked at, doesn’t she? Tell the truth!”
_{^{- Harry Potter and the Half-Blood Prince, Chapter 13 (The Secret Riddle)}}

She suspected he was the cause of quite a few odd incidents, and it’s clear she’s at least asked him about them, so she may have also tried to get him to stop.

“You can’t kid me! The asylum, that’s where you’re from, isn’t it? “Professor”, yes, of course – well, I’m not going, see? That old cat’s the one who should be in the asylum. I never did anything to little Amy Benson or Dennis Bishop, and you can ask them, they’ll tell you!”
_{^{- Harry Potter and the Half-Blood Prince, Chapter 13 (The Secret Riddle)}}

She of course wouldn’t know about magic, but it’s possible she tried to stop him from “bullying”.

Harry tried to convince him to feel some remorse at their battle.

After ‘coming back’ from Kings Cross, Harry tries to convince the Dark Lord to feel remorse.

“Yeah, it did,’ said Harry. ‘You’re right. But before you try to kill me, I’d advise you to think about what you’ve done … think, and try for some remorse, Riddle …’

‘What is this?’ Of all the things that Harry had said to him, beyond any revelation or taunt, nothing had shocked Voldemort like this. Harry saw his pupils contract to thin slits, saw the skin around his eyes whiten.

‘It’s your one last chance,’ said Harry, ‘it’s all you’ve got left … I’ve seen what you’ll be otherwise … be a man … try … try for some remorse …”
_{^{- Harry Potter and the Deathly Hallows, Chapter 36 (The Flaw in the Plan)}}

He’d seen what the Dark Lord would become, and tried to give him a chance to save himself.

Everyone else either was charmed by Tom or was terrified of him.

Other than Dumbledore, the Hogwarts staff all liked Tom Riddle, and Tom did a very good job of concealing things from them, so they’d have no reason to be suspicious of him.

“However, if he was frightening or impressing fellow Slytherins with displays of Parseltongue in their common room, no hint of it reached the staff. He showed no sign of outward arrogance or aggression at all. As an unusually talented and very good-looking orphan, he naturally drew attention and sympathy from the staff almost from the moment of his arrival. He seemed polite, quiet and thirsty for knowledge. Nearly all were most favourably impressed by him.”
_{^{- Harry Potter and the Half-Blood Prince, Chapter 17 (A Sluggish Memory)}}

The students were too scared of him to talk to Dumbledore about him when Dumbledore came asking them - they’d likely be much less willing to tell Tom Riddle himself anything.

“I have not been able to find many memories of Riddle at Hogwarts,’ said Dumbledore, placing his withered hand on the Pensieve. ‘Few who knew him then are prepared to talk about him; they are too terrified.”
_{^{- Harry Potter and the Half-Blood Prince, Chapter 17 (A Sluggish Memory)}}

For different reasons, none of them would want to try talking to Tom Riddle.