Which Norwegian king put a definitive end to their civil war era?

Haakon IV Haakonsson (c. March/April 1204 – 16 December 1263), sometimes called Haakon the Old in contrast to his son with the same name, and known in modern regnal lists as Haakon IV, was the King of Norway from 1217 to 1263. His reign lasted for 46 years, longer than any Norwegian king since Harald I. Haakon was born into the troubled civil war era in Norway, but his reign eventually managed to put an end to the internal conflicts.

At the start of his reign, during his minority, his later rival Earl Skule Bårdsson served as regent. As a king of the birkebeiner faction (a Norwegian rebellious party), Haakon defeated the uprising of the final bagler royal pretender, Sigurd Ribbung, in 1227. He put a definitive end to the civil war era when he had Skule Bårdsson killed in 1240, a year after he had himself proclaimed king in opposition to Haakon. Haakon thereafter formally appointed his own son as his co-regent.

Under Haakon's rule, medieval Norway is considered to have reached its zenith or golden age. His reputation and formidable naval fleet allowed him to maintain friendships with both the Pope and the Holy Roman Emperor, despite their conflict. He was at different points offered the Imperial Crown by the Pope, the Irish High Kingship by a delegation of Irish kings, and the command of the French crusader fleet by the French king.