Itzcoatl is the ruler of Tenochtitlan listed as the founder of the Triple Alliance.
Itzcoatl became the fourth tlatoani, or ruler, of Tenochtitlan in 1427. His reign began during a crisis: the Mexica were still subject to the Tepanec power centered at Azcapotzalco. Itzcoatl allied with Nezahualcoyotl of Tetzcoco and Totoquihuaztli of Tlacopan, helping defeat the Tepanecs and overturn their regional dominance.
After that victory, the three city-states formed the alliance later known as the Aztec Triple Alliance. It became the political foundation of the empire commonly called the Aztec Empire. Although the alliance had three founding rulers, Itzcoatl is singled out in this question because he was the ruler of Tenochtitlan and the key Mexica leader behind its creation.
The other choices were later rulers of Tenochtitlan. Axayacatl ruled during the empire’s expansion, Tizoc had a short reign after him, and Cuitláhuac ruled briefly during the Spanish invasion in 1520. None founded the alliance.