Argentinos celebrated their third title and first in 25 years after a 2-1 win at Huracan while fans of the home team, who had had two players sent off, fought with police on the terraces after the final whistle.
Argentina midfielder Juan Mercier put Argentinos ahead in the 23rd minute and Facundo Coria ended a sweeping counter-attack for the second in the 77th. Alan Sanchez pulled one back for nine-man Huracan with a brilliant goal in the 88th.
Huracan centre back and captain Paolo Goltz was dismissed in the 66th minute and Pablo Jerez in the 83rd.
"Without a doubt our greatest virtue was that we played very good football," midfielder Coria told reporters.
Argentinos coach Claudio Borghi, a member of captain Maradona's 1986 World Cup-winning squad, added the title to those he lifted as a player with the club in 1984 and 1985.
Fans also caused trouble at Colon, where Estudiantes de La Plata, the only team who could have snatched the title from Argentinos, crushed the home side 4-1 with a hat-trick by striker Mauro Boselli, championship top scorer with 13 goals.
Estudiantes fans, who began throwing stones and other objects over the high perimeter fence on the pitch near the end of the match and looking for fights, were doused by powerful police hoses on a chilly autumn evening.
LOST GRIP
The reigning South American champions lost their grip on the championship the previous weekend when they were held 0-0 by Rosario Central and Argentinos came from 3-1 down to beat Independiente 4-3 and go a point ahead.
Argentinos finished the 19-match championship with 41 points. Estudiantes took 40, surprise team Godoy Cruz from Mendoza 37 and Independiente 34.
Banfield, winners of the Apertura in the first half of the season, finished fifth with 32 points. Apertura runners-up Newell's Old Boys, the team that took most point overall in the season without winning a title, were sixth with 30.
The championship stood out too for the poor showing by four of the big five Buenos Aires teams, notably River Plate and Boca Juniors, who finished 13th and 16th. Independiente were the exception.
River bowed out in a 5-1 home defeat on Saturday by Tigre, who had never won before at the Monumental, which doubles as Argentina's national stadium.
Boca, for whom Juan Roman Riquelme and Martin Palermo had their off-field differences and shone intermittently on the pitch, ended up with the worst defence having conceded 35 goals in their 19 games.
