It is Bill who eventually destroys It, engaging It in the Ritual of Chüd in both 1958 and 1985, and eventually killing It's physical form by ripping its heart out.
The spider-clown shrinks as the Losers hurl taunts at It, until it's tiny and weak enough that they pluck out its heart and squash it into nothingness. In the end, they defeat Pennywise by, uh, making him feel really bad about himself.
Accordingly, the gang force Pennywise to become small and weak, after which they're able to remove his still-beating heart and crush it in their hands, finally ending his reign of terror.
Pennywise shrivels to the size of a baby and Mike rips out his heart. The Losers crush it in their hands together and Its form disintegrates into dust, bringing the whole cave down with him. Eddie Kaspbrak dies.
Now, when the Losers crushed IT's heart while in its spider form, they killed IT's physical form and severed its connection to Derry, thus why the town was destroyed, but the true entity still lives in another plane of existence.
He also almost approaches the Losers to join them but decides against it. By doing this, he seals his fate and joins Henry and Belch in following the Losers into the sewers, where the three encounter It in the form of Frankenstein's monster, who kills Vic by decapitating him.
According to It, when humans got scared, "all the chemicals of fear flooded the body and salted the meat". This is why he prefers to feast on children -- their fears are simple, pure, and powerful compared to the complex, pathological fears of adults.
In the novel, It's origins are nebulous. He took the form of a clown most frequently, Mr. Bob Gray or Pennywise, but his true form is an ancient eldritch entity from another universe who landed in the town that would become Derry by way of an asteroid and first awoke in 1715.
Pennywise's strength is also his weakness. For example, if he were to take the shape of a werewolf (as he does in the novel), silver bullets would harm him.
Its natural enemy is the "Space Turtle" or "Maturin", another ancient dweller of King's "Macroverse" who, eons ago, created the known universe and possibly others by vomiting them out as the result of a stomachache.
That is, when Pennywise morphs into a werewolf, he is subject to the same weaknesses as a werewolf, including silver slugs. In both the original novel and made-for-television adaptation, Pennywise is weakened using silver bullets melted down from earrings.
After the Losers' Club defeat Pennywise, they get lost in Derry's sewer system. After coming to the realisation that they can't escape without being unified, Beverly — the single female member — decides she needs to have sex with the six boys.
It also known as Pennywise the Dancing Clown was the titular main antagonist of the Stephen King novel and miniseries of the same former name. He was an evil and demonic entity who would almost always disguise himself as a clown to attract children so he can capture and kill them as they are an easier target.
Pennywise's Kills Add Up Over Time
The number is then multiplied by the number of times Pennywise has awakened -- once every 27 years throughout the 270-year history of Derry, equaling ten times -- to come up with a final tally of between 12,000 and 18,000 dead.
Another explanation is connected to the Turtle and the cosmic side of IT and Stephen King's Macroverse, suggesting the Losers as the “chosen ones” that were guided and thus protected to an extent by Maturin, the only creature IT is afraid of.
The Losers confront Pennywise on how they've overcome their fears, and are no longer scared of the entity, causing It to shrink to a small weakened Pennywise. Mike rips out It's heart, which he and the Losers crush with their bare hands, finally killing It.
So instead of returning to Derry with the rest of his old friends, he made the calculated decision to kill himself, just so it would be easier for his childhood chums to murder a demon clown.
Chapter Two reveals that Bowers washed out in the Barrens (surrounded by children's body parts, naturally) and when he made it back home, he was immediately arrested for the murder of his father.
The audience comes to find out that Richie, played by veteran comedian Bill Hader, is gay during his singular quest to retrieve a childhood artifact for the Ritual of Chüd.
In the novel, It's origins are nebulous. He took the form of a clown most frequently, Mr. Bob Gray or Pennywise, but his true form is an ancient eldritch entity from another universe who landed in the town that would become Derry by way of an asteroid and first awoke in 1715.
The Deadlights are orange writhing lights that exist in Todash Darkness. Pennywise uses its Deadlights to break a person's mind because one look at the Deadlights will make a person go insane due to it not being able to be comprehended by a human mind.
In It: Chapter Two, Stan commits suicide upon hearing of It's return in 2016, much like in the novel and miniseries. It later tauntingly reveals this to the other Losers when they gather at a Chinese restaurant and Beverly reveals she has had nightmares of Stan's suicide for years.
That is, when Pennywise morphs into a werewolf, he is subject to the same weaknesses as a werewolf, including silver slugs. In both the original novel and made-for-television adaptation, Pennywise is weakened using silver bullets melted down from earrings.