Canonically, the strongest Archon is Zhongli; he is also the oldest Archon. However, an Archon's strength is directly correlated to the amount of control exerted upon their respective regions. Since Liyue is the largest region as of version 2.7, and due to his immense natural power, Zhongli was the strongest Archon. However, he relinquished his command over Liyue and handed it to the Liyue Qixing. Therefore, the strongest Archon has to be the Tsaritsa since she exerts the next highest amount of control and authority, not to mention that she also has the best military in all of Teyvat. With the technological advances, the amount of control that she has, and the amount of land she watches over, the Tsaritsa and her hands-on approach to being an Archon will be a force to be reckoned with.