What is the name of the Maya ruler who reigned at Tikal during its greatest power?

The Maya ruler who reigned at Tikal during its greatest power was Jasaw Chan K'awiil I.

Jasaw Chan K'awiil I ruled Tikal from 682 to 734 CE, taking the throne after a long period in which the city's historical record was relatively quiet. His reign is associated with Tikal's major political and military resurgence during the Late Classic period.

In 695, Tikal defeated its powerful rival Calakmul, a victory widely seen as a turning point that restored Tikal's influence in the Maya lowlands. Jasaw Chan K'awiil is also linked with Tikal's monumental Temple I, where he was buried, and Temple II, associated with his wife.

He is sometimes confused with his successor, Yik'in Chan K'awiil, who was also an important ruler and continued Tikal's building and political expansion. Older sources may call Jasaw Chan K'awiil “Ruler A” or “Ah Cacao,” names connected with earlier stages of deciphering Maya inscriptions.