This page explains how to start and complete the The Road to Respect side quest.
How to Start the Quest
Go to Goron City and talk to Fugo to start the quest. He says that he needs to defeat the Igneo Talus at Darunia Lake to earn Rohan's respect.
How to Complete the Quest
The Igneo Talus is northeast of Shae Mo'sah Shrine. You will need to use the rail cart north of the shrine to get there. To use the cart, stand on it and put a round bomb in the rear compartment, then detonate the bomb. (The rear compartment will contain the blast, so you won't take damage.)
When the cart reaches solid ground north of Darunia Lake, go west along the lower path and make your way clockwise around Darunia Lake. The Igneo Talus is on the west side of Darunia Lake.
Afterward, go talk to Fugo in Goron City and agree to sell the achievement, and he will give you a Silver Rupee.