Here are a selection of the worst of the worst.

Tobias Snape

Although we don’t know much about Severus Snape’s father, we have a bad feeling about him based on one remark from a young Severus to a young Lily: ‘he doesn’t like anything, much’. There is also the insinuation that Tobias Snape, a Muggle, was not a fan of magic despite having a child with a witch. Again, as Snape says, he doesn’t like anything much. We also know that Snape’s parents had frequent arguments – and when a young Lily asks Snape how ‘things are at your house’ – Snape simply responds with a ‘little crease’ between the eyes. We can only speculate how bad things were at home for Snape, but these small signals do make us wonder.

Vernon Dursley

The thing with Mr Vernon Dursley was that he firmly believed that everything he did, especially with regards his son, was right. But in actuality – Vernon was feeding Dudley with the same flaws he had within himself, and by spoiling Dudley with everything he ever wanted, he created a materialistic monster: an arrogant, petulant bully. How could he possibly have predicted that? Thankfully, it did turn out that Dudley had a thoughtful streak in him somewhere, as discovered when he shook Harry’s hand upon his departure from Privet Drive – so his father-taught morals can’t have been 100-per-cent poor.

‘You did not do as I asked. You have never treated Harry as a son. He has known nothing but neglect and often cruelty at your hands. The best that can be said is that he has at least escaped the appalling damage you have inflicted upon the unfortunate boy sitting between you.’ Both Aunt Petunia and Uncle Vernon looked around instinctively, as though expecting to see someone other than Dudley squeezed between them. ‘Us – mistreat Dudders? What d’you –?’ began Uncle Vernon furiously, but Dumbledore raised his finger for silence, a silence which fell as though he had struck Uncle Vernon dumb.
Harry Potter and the Half-Blood Prince

Lucius Malfoy

Here’s another paterfamilias motivated only by his desire to see his son succeed – only, since he did this by means of cruelty, we’re rather less inclined to let his behaviour slide. Lucius was proud of Draco, certainly, but rarely displayed it with affection, and if he’d turned his tongue to sweetness even occasionally, his son might have grown up less obsessed with status and power.

It was Lucius who set Draco against Harry, and Lucius who led his son under the wing of the Dark Lord, and Lucius who, until the very last minute, prioritised power over his family. A bad dad, if ever there was one.

Marvolo Gaunt

We encountered Marvolo only briefly between the pages of these tales, but the impression we got was not good. He attacked a Ministry employee (who was a bit smug and annoying, but still), he physically abused his subdued daughter, and he made it clear that he valued purity of blood over any redeeming human quality.

We might have had nothing more than a snapshot of this man, but suffice to say he was an abominable father and a travesty of a wizard. That he died, after a period in Azkaban, alone and bereft, does nothing to redeem him. And we think it’s fair to say that it was his blood running through Voldemort’s veins that made the Dark Lord who he was: cruel, prideful and vengeful. ‘Is it true?’ said Gaunt in a deadly voice, advancing a step or two towards the terrified girl. ‘My daughter – pure-blooded descendant of Salazar Slytherin – hankering after a filthy, dirt-veined Muggle?’
Merope shook her head frantically, pressing herself into the wall, apparently unable to speak.
Harry Potter and the Half-Blood Prince

Bartemius Crouch (Sr)

There was much about Bartemius that was laudable. He was a senior official, had a very good moustache, spoke more than 200 languages (even if Troll is mostly just grunting), and we can’t blame ‘Weatherby’, sorry, Percy, for having thought highly of him.

Peer beneath the carefully-clipped moustache, though, and Crouch was revealed to be a man motivated by greed and anger, incapable of feeling pity for his own family. Though there’s an argument to say that Barty Jr was demonic from the offing, and that Bartemius’s brutal style of parenting was born of necessity, one need only look to a house-elf to see the flaw in that argument. Barty Sr’s treatment of Winky might not have spoken directly to his capacity as a father, but still – it doesn’t bode well when a wizard forces his house-elf to perform tasks he knows she loathes, then immediately dismisses her when she’s accused of performing a misdeed he knows her not to have done.

If nothing else, we can say that in the end, Crouch paid the price of his actions, spending his final days under the control of his maniacal son, and finally slain by his own flesh and blood. Though we shrink from advocating murder, obviously, we cannot help but conclude that patricide was a fitting end for this assiduous law-abider who broke every basic rule of parenting.

‘Did Crouch try and get his son off?’ Hermione whispered.
Sirius let out a laugh that was much more like a bark. ‘Crouch let his son off? I thought you had the measure of him, Hermione? Anything that threatened to tarnish his reputation had to go, he had dedicated his whole life to becoming Minister for Magic. You saw him dismiss a devoted house-elf because she associated him with the Dark Mark again – doesn’t that tell you what he’s like? Crouch’s fatherly affection stretched just far enough to give his son a trial and, by all accounts, it wasn’t much more than an excuse for Crouch to show how much he hated the boy ... then he sent him straight to Azkaban.’
Harry Potter and the Goblet of Fire