Andreas "Anthe" Kren (which may be abbreviated to AAK) is an Austrian Doomer best known for his speedrunning, especially in the Nightmare! categories. Adam Hegyi has written that "many consider him the most talented player of all time."
Anthe set over 100 Compet-n records in the late 1990s. His first NM100S demos were recorded with the additional restriction that only the pistol and shotgun be used, yet in some cases were still the fastest ever submitted. 
According to Anthe himself, his nickname "is the Viennese (drunk) version of Andi which is short for Andreas".  The abbreviation "AAK" is also derived from the name of a former girlfriend.