so really digging down into all the major post WWII European and Global true cups, there were/are these 9:
European Cup / UEFA Champions League
UEFA Cup / UEFA Europa League
UEFA Cup Winners' Cup
UEFA Intertoto Cup
Inter-Cities Fairs Cup
UEFA Europa Conference League
European Super Cup / UEFA Super Cup
Intercontinental Cup
FIFA Club World Cup
No club can win all 9, Juve comes the closest, but they blew 2 Inter-Cities Fairs Cup (now defunct) finals
European Cup / UEFA Champions League 2 1984–85, 1995–96
UEFA Cup Winners' Cup 1 1983–84
UEFA Cup / UEFA Europa League 3 1976–77, 1989–90, 1992–93
European Super Cup / UEFA Super Cup 2 1984, 1996
UEFA Intertoto Cup 1 1999
UEFA Europa Conference League None, still can win it as it is brand new
Inter-Cities Fairs Cup None, were Runners Up 1965, 1971, and it is defunct so they cannot win it
Intercontinental Cup 2 1985, 1996
FIFA Club World Cup None but still can win it