Are the sins of even the vilest wicked people already atoned for?
Yes. When Christ died, God laid on Him all sin from Adam to the last person in time and judged it, pouring out His wrath. Therefore even the vilest wicked people's sins are already atoned for and paid for; they face eternal doom only by rejecting the Gospel.
Les explains that Christ's crucifixion was not unique merely as a crucifixion, since thousands were crucified. It was unique because the Creator God Himself took on human flesh and went to the cross. There God poured out all His wrath for sin, laying on Christ the sin of all people from Adam to the last person who will live in time, and God judged it. Therefore even the vilest mafia member or wicked person has sins already atoned for and paid for. The only reason such a person goes to eternal doom is rejection of salvation, and rejecting the Gospel is the one sin that puts a person in eternal doom. The sin debt has been paid and finalized once and for all, which is why Paul burned to get the Gospel of salvation to lost people.