Jerkass Woobie: Al Simmons, the main character himself. He ended up this way because he died, was sent to Hell for murdering innocents and being an abusive husband and got his powers from making a deal with a demon. In other media, people have been labelled asshole victims for less.
Love to Hate: Mammon. He's such a smug, thoroughly detestable prick, but he displays a certain cunning and penchant for manipulation that just makes hating him for it satisfying.
Mainstream Obscurity: Despite being one of the most iconic characters of the 1990s, actual familiarity with anything about Spawn besides his character design and the grim-and-gritty tone of his stories is very low.
Nightmare Fuel: Almost everything in the comic. Even some of the regular humans are scary just to look at.
Big-Lipped Alligator Moment: The scene with Clown wearing a cheerleading costume doing a dance number which comes out of nowhere, serves no purpose and which the protagonist doesn't even see happening. The devil himself ends the moment by dragging the clown back to hell to tell him to quit fucking around.
Harsher in Hindsight: Spawn is very close with Cyan, with the obvious implication that she's his daughter. But later in the comics, we learn that she is not Al's daughter and he had been in denial about the fact that he was an abusive husband who caused Wanda to miscarry when she was pregnant with his child. Though Resurrection does mitigate this by revealing the abuse was actually a lie itself to manipulate Al.
Especially the last third of the film. Clown has convinced Jason Wynn have the trigger to a bio weapon implanted that will be set off if his heart stops beating, which he plans to have happen by having Al Simmons do the deed. Later Simmons goes to rescue Wanda and her family when Wynn shows up for little to no reason and then Clown starts a fight with Simmons which prevents him from being able to seek to kill Wynn.
Malebolgia's master plan is to choose a skilled operative to lead Hell's army and jump-start the apocalypse. In order to do that he has to have that operative killed, sent to Hell, and then make a deal with him to turn him into a Spawn and then return him to Earth to kill Jason Wynn. The entire plan hinges on getting Simmons to kill Wynn, but Simmons still has a conscience and a living family to consider, and so the plan fails. If Malebolgia had instead simply chosen someone skilled who was completely amoral and had no human connections, and was possibly also power-hungry, this plan would have gone off without a hitch. In fact, if Malebolgia had just selected Jessica Priest to be Spawn instead of Simmons, the forces of evil would have won. She would have been perfect.
As seen in the below trope, the CG that the movie indulges in so heavily looks absolutely terrible nowadays. It's pretty hard to care about the drama of the plot, or even to enjoy the fight scenes, when the CG for your dark, gritty, anti-hero movie looks worse than the animation in ReBoot.
Special Effect Failure: The computer effects—the majority of which were done by ILM—have not aged well since the movie's 1997 release. Spawn's cape only appears when in use (either for dramatic effect or when he makes use of its shapeshifting power), since it was difficult to animate. Plus, Malebolgia'snote Not done by ILM, but by another company. mouth does not remotely sync with his words, and Hell just looks like something out of a (subpar, mind you) Playstation 1 game. It's especially jarring considering the great practical and make-up effects for Spawn and the Clown.
Squick: You know the part where Clown eats a piece of pizza he found in a dumpster? The one covered in maggots? Leguizamo really ate that.
Let's not forget about Clown sharting himself, and then showing his soiled underwear afterwards. Disgusting. Even the hard boiled Spawn/Simmons is abhorred by it.
Cult Classic: Thanks to being much Darker and Edgier than any other Western Animation of its timenote as well as any that came after for that matter. and among one of the only Western Animation series to bring such genuinely mature and sophisticated themes to the table, the Spawn animated series fits this trope like a glove.
Evil Is Cool: Clown/Violator, he's such a deplorable antagonistic figure but you can't help but enjoy how much he reviles in his depravity.
Hilarious in Hindsight: One of the bums in the first season likens Spawn's appearance to a vampire. He later fights a vampire in season 3 that looks nothing like him.
The comic already had some scary stuff, but Violator's transformation (which depicts him as tearing through the body he has like its paper) and Creepy Monotone arguably make him more terrifying here than in the comics.
Some of the human villains also count. Namely, Billy Kincaid. Especially when he kidnaps Cyan. His dialogue and behavior when he's talking to her make's him sound like a child molester. Not helped by the eerie echo his voice has.....
Billy Kincaid: Time to have that ice cream. Such a pretty one. Do you like the music? I like the music very much. Would you like to you dance? Just you and me. But first...I scream, you scream. We all scream for ice cream! Chocolate pecan, strawberry whirl! All...very good!
Hell, even Spawn gets one in the animated series, he basically had Chapel, his former partner and killer, dead to rights and Chapel realizing who Spawn is, tried to commit suicide, but fails since his gun has no bullets left. Chapel literally begs Spawn to kill him, knowing what he learned will forever haunt him, what does Spawn do? He let Chapel live, leaving him to wander away crying, knowing that death would have been kinder.
Spawn (Al): No. I'm going to let you live, longer than you like.
Paranoia Fuel: Walking into the wrong alley just might get you killed by a Hellspawn and that might even be the least of your troubles.
Strangled by the Red String: The kiss Jade shares with Spawn and subsequent implied relationship between them... really comes out of nowhere. Even when she was shown to be sympathetic towards Spawn and having doubts about her job to kill him, they only briefly met in person once before and there was never any mutual attraction implied. Even Spawn and the Vampiress showed more chemistry, at least before she tried to kill him.