Question: The Orthodox stance was used by the last boxer in what weight class to hold the undisputed champion title?

Context paragraphs:
Professional wrestling weight classes: In professional wrestling, a weight class is a standardized weight range for the wrestlers.  The top class in almost every promotion is heavyweight, but super heavyweights exist.  Weight class matches in modern-day American professional wrestling are rare, but weight class championships still exist.  However, Japanese professional wrestling, Mexican wrestling and British wrestling use the weight classes more seriously.

Evander Holyfield: Evander Holyfield (born October 19, 1962) is an American former professional boxer who competed from 1984 to 2011.  He reigned as the undisputed champion in both the cruiserweight and heavyweight divisions, being the first and to date only boxer in history to do so, which earned him the nickname of "The Real Deal".  Holyfield is the only four-time world heavyweight champion, having held the WBA, WBC, IBF, and lineal titles from 1990 to 1992; the WBA, IBF, and lineal titles again from 1993 to 1994; the WBA title from 1996 to 1999; the IBF title from 1997 to 1999; and the WBA title for a fourth time from 2000 to 2001.

Moruti Mthalane: Moruti Mthalane (born 6 October 1982), is a South African professional boxer with orthodox stance who goes by the nickname of "Babyface".  His professional record includes 27 fights: 25 wins (16 knockouts), and 2 losses.  He lives in Johannesburg, Gauteng, South Africa.  He is the current IBO Flyweight champion and a former IBF Flyweight champion.

Weight class (boxing): A weight class is a measurement weight range for boxers.  The lower limit of a weight class is equal to the upper weight limit of the class below it.  The top class, with no upper limit, is called heavyweight in professional boxing and super heavyweight in amateur boxing.  A boxing match is usually scheduled for a fixed weight class, and each boxer's weight must not exceed the upper limit.  Although professional boxers may fight above their weight class, an amateur boxer's weight must not fall below the lower limit.  A nonstandard weight limit is called a catch weight.

Michael Seals: Michael Seals (born July 1, 1987) is a professional light heavy weight boxer from Atlanta, Georgia.  He is 6 feet 3 inches tall,weighs approximately 175 lbs, and fights in the orthodox stance.  His professional record is 18-1, with 14 wins by knockout.

Lennox Lewis: Lennox Claudius Lewis, {'1': ", '2': ", '3': ", '4': "} , {'1': ", '2': ", '3': ", '4': "} (born 2 September 1965) is a former professional boxer who competed from 1989 to 2003.  He is a three-time world heavyweight champion, a two-time lineal champion, and remains the last heavyweight to hold the undisputed title.  Lewis holds dual British and Canadian citizenship; as an amateur he represented Canada at the 1988 Summer Olympics, winning a gold medal in the super-heavyweight division after defeating future world champion Riddick Bowe in the final.

Cecilia Brækhus: Cecilia Carmen Linda Brækhus (born 28 September 1981) is a Norwegian professional boxer and former kickboxer.  In boxing she has reigned as the undisputed female welterweight champion since 2014, and is the first woman in any weight class to hold the WBA, WBC, IBF, and WBO titles simultaneously.  Additionally she is one of only four boxers in history, female or male, to hold all four titles simultaneously, along with Bernard Hopkins (2004–2005), Jermain Taylor (2005), and Terence Crawford (2017).

Orthodox stance: In combat sports such as boxing, an orthodox stance is one in which the boxer places his left foot farther in front of the right foot, thus having his weaker side closer to the opponent.  As it favors the stronger, dominant side—often the right side, see laterality—the orthodox stance is the most common stance in boxing.  It is mostly used by right-handed boxers.  Many boxing champions—such as Jack Johnson, Anthony Joshua, Marco Antonio Barrera, Rocky Marciano, Ingmar Johansson, Roberto Durán, Floyd Mayweather Jr., Muhammad Ali, Amir Khan, Peter Buckley, Johnny Tapia, Mike Tyson, Larry Holmes, Lennox Lewis, and Wladimir Klitschko —fought in an orthodox stance.

Lineal championship: In combat sports where champions are decided by a challenge, the lineal championship of a weight class is a world championship title held initially by an undisputed champion and subsequently by a fighter who defeats the reigning champion in a match at that weight class.  In professional boxing, the lineal champion is informally called "the man who beat the man".  Champions recognized by sanctioning bodies such as the World Boxing Association (WBA) or World Boxing Council (WBC), or the Ultimate Fighting Championship (UFC) may vacate their title voluntarily, or be stripped of the title for breaching the sanctioning body's regulations or contracts.  There will thus be a breach of continuity in the list of sanctioned champions which the lineal championship is intended to prevent.  However, there is no single canonical list of lineal champions at any weight class, because there is no agreed upon method of determining the starting point for each lineage and conflicting opinions on what to do when the current champion retires or moves to a different weight class, although there is agreement that any stripping of a title be discounted.

Undisputed champion: In professional boxing, the undisputed champion of a weight class is a boxer who is recognized as the world champion at that class by each boxing organization.

Supporting paragraphs: Orthodox stance Lennox Lewis
Answer: heavyweight