It's generally believed that the mob never retaliates against rats. While it rarely happens, especially nowadays, it's simply not true that they always go unharmed. I'll list a few examples below, not in chronological order.

1) Mario Riccobene, associate of the Bruno Family. After returning to his old lifestyle in 1993, he was murdered by his old associates for cooperating as a government witness

2) Joseph Barboza, aka The Animal, associate of the Patriarca Family. On February 11, 1976, The Animal left Chalmas' San Francisco apartment; as he was walking to his car, he was hit by 4 shotgun blasts at close range. 

3) Joseph D'Amico, aka The Mook, turncoat soldier in the Bonanno Family. The Mook apparently thought that he could walk the streets of Little Italy untouched. He was wrong. When mob associate Thomas Leonessa, aka Tommy Stacks, saw The Mook, he confronted him & called him a rat. Tommy Stacks was then caught on surveillance footage punching & kicking The Mook & then smashing his cell phone. The Mook was hospitalized for 2 days after the beating. This was in 2016.

4) Frank Bompensiero, aka The Bomp, captain in the Dragna Family. On February 10, 1977, The Bomp was shot to death at close range with a silenced .22 caliber handgun while walking home after using a pay phone outside an Arco Station in the Pacific Beach neighborhood of San Diego.

5) Christopher Castellano, I'm assuming associate of the Ndrangheta/Genovese Family due to who was involved. Castellano, in exchange for being freed on bail in New York in March 2009, agreed to “sing” to U.S. prosecutors. Castellano was shot and killed on July 4, 2010, in Queens and the homicide case is yet to be solved.

6) Frank Lagano, soldier in the Lucchese Family. Lagano was shot execution-style in the parking lot of his East Brunswick diner on April 12, 2007.

An attempt was made to look for and kill Salvatore Gravano, aka Sammy the Bull, turncoat underboss of the Gambino Family, in 1999. Same thing happened with Sean Richard, associate of the DeCalvacante Family, in 2016

For those of the opinion that it can't or won't ever happen, never say never. Any other examples? We can include other countries as well.

Mafia snitch shot dead in parking lot – Testified against Catania’s Santapaola Clan in 1990s https://gangstersinc.org/2019/04/24...ainst-catanias-santapaola-clan-in-1990s/

Brother of Mafia snitch was murdered after he had asked to be removed from witness protection program https://gangstersinc.org/2019/01/02...removed-from-witness-protection-program/

Other criminal organizations have also been able to successfully get rid of snitches.

There's the case of Lucchese soldier Anthony DiLapi who fled to California and was killed by Joey D'Arco on order form Amuso and Casso. I don't think he cooperated though. He just left the Mob and was eventually found by the infamous Mafia Cops.

Willie Boy is another one. Not the smartest guy staying around in plain sight after Gotti “promised” him he wouldn’t retaliate

Good one! Can't believe I forgot about him. I don't think Anthony DiLapi counts here.

Leonardo Vitale was a mafioso that decided of collaborate in 1977. Called the Valachi of Altarello (a Palermo neighborhood) but was too soon and given that the "mafia don't exist" he ended up in a mental asylum and killed in 1984 after get out.

Claudio Sicilia was a member of The Magliana Gang that flipped in 1985 and let to 60 arrests. After the collaboration was let without protection and was killed in 1991.

James "Whitey" Bulger boss of Winter Hill Gang from 1979 to 1995 and long time informant for FBI to destroy Boston Mafia.
Ended killed in a very fiere mode by lifer Geas and mobster DeCologero.

Wow amazing I forgot about Whitey Bulger, memory's bad lol

Whitey Bulger and his art teacher shortly before get whacked.

didnt they kill Tomasso Buscettas whole family for ratting?

These guys get assaulted more often than you think. If Dom Cicale were to venture into certain pockets of the Bronx, he probably would go home with a busted lip

More like a busted skull! Lol.

No, he actually flipped due to them killing his relatives, not the other way around.

The fact is that Buscetta was a lone wolf that wanted the money and the women that the power so when begun the second mafia war,he stayed neutral and Riina ordered to kill his relatives for force him to turn back in Palermo and try to revenge.
But he does nothing but after was arrested and feared the extradition in italy decided to flip for avoid being killed in prison and together revenge his relatives.

Lea Garofalo,ndrangheta collaborator of justice. Killed in 2009 by his husband her body dissolved in acid.

Abe "Kid Twist" Reles.

Good one.

Prior to the 1960's they were would likely be killed if they ratted, especially member. Since then each decade it went to the point where by 2000 they could walk around openly after ratting. Exceptions? Maybe one or 2, many more ratted than that number. I am referring to The American Mafia, not gangs in Italy, Sweden, or wherever else.