Visenya the first

Or "The peaceful queen". She was not terrible, even quite good... but her heritage politics.... ruined house Targaryen's mightiness. Her reign was a "Golden age", but mostly due to her grandmother's wisdom in previous one. Oftenly she is compared to Byzantine Emperor Manuel Komnenos. Both of them ruled in a stable era created by precedessors, but did nothing to prevent conflict from beginning after their death...