Koutetsu no Łucja

In Poland, a country powered by steam, the new technology was also applied to combat. Wearing steam armor, warriors compete in martial arts tournaments to fight for the title of "Knight King," a badge of strength. A young girl named Łucja joined the tournament, wielding two arms of steam armor. The difference between Łucja and the other fighters is that Łucja is otherwise unarmed, using only her fists and the strength of her single blow to defeat her opponents.

(Source: Comic Border, translated)

Note: includes 3 bonus chapters in Vol. 3.