American Thugs

American Thugs (アメリカの刺客) was a group of three assassins from the USA, tasked with hunting down Denji’s heart.

History
Like their title suggests, they are three related brothers, consisted of the unnamed eldest brother, Joey being the middle brother and Aldo being the youngest brother. Due to the incident with the gun devil that killed their parents and their grandmother, they ended up becoming an assassin as their way of living. They seem to be very confident, perceiving themselves as immortals.

International Assassins Arc
The three brothers were employed by the US Government to find, and retrieve the chainsaw heart back to the USA for two million dollars. The elder brother reaffirms Aldo that they are immortal, and proceed to Japan. Three Devil Hunters from Japan, Michiko Tendo, Yutaro Kurose and Subaru, are driving in a vehicle on the way to be additional guards for Denji, are stopped by road spikes. The three brothers emerge, and they fatally shoot the passengers. The eldest brother uses the Skin Devil to change into one of the passengers, Yutaro Kurose.

The eldest, now presenting as an injured Yutaro, hurriedly informs Kobeni and the Violence Devil, Galgali to call a phone to HQ about the incident that happened prior. The two hunters, and the disguised brother meet up with Denji and the rest of the squadron. He gets informed that Denji is the Chainsaw Man, and assures Denji that he will protect him. Power drives into him and Denji while driving Kobeni's car. The unnamed brother gets launched into a fence pole and hits his head, killing him. His disguise deactivates, and he is recognized as one of the three hitmen from the USA. The squadron learn that since one of the brothers are in Japan disguised, that must mean that the other two are as well. Aldo and Joey are in the crowd during this and react in horror.

The remaining two brothers retreat to an alleyway in shock and mourning of their deceased brother. Joey in anger begins to return to the crowd, but is killed by Hirofumi Yoshida. Yoshida dismisses Aldo as he is still in disguise.

Having no place to go, Aldo disguised as Kurose finds a picture of Kurose, Tendo and Tomono and visits Tomono. They spend the night talking about their past, but looking at a picture of Kurose, Aldo gets sick. Later that night while trying to fall asleep, Tomono tells "Kurose" that he plans on quitting his job and wonders if Kurose would start a secondhand clothing store and quit Devil Hunting. He explains that if he continue being a Devil Hunter, he will eventually die like his older brother and needs to look at his parents. Tomono then wonders what his brother will say about this and Aldo remembering his own brothers tell him that a pro gets the job done, making Tomono wonder if Kurose's brother would actually say something cool like that.

Aldo continues to the department store where Denji is at, and emerges when Quanxi and her fiends are fighting Denji and his guards. He shoots and misses Denji, but aims for Long, who is restraining Denji. He shoots her until he gets thrown out of the department store by Quanxi, and lands on Kobeni's car. He witnesses the Hell Devil sending everyone in the department store to Hell.

Aldo is seen at the end of the arc in the crowd of puppets, repeating "Halloween". He is possibly mind controlled, but judging from his facial expressions it is likely he is merely acting as to survive.