Was Zeus the most powerful god?

As a "god" in Greek mythology, Zeus was no more or less than any other god could be considered; he won and lost in battles and arguments(his early loss against Typhon being one of the most notable and significant), and was subject to the will of the Fates like anyone else, and in this respect, he is not a "force of nature" type deity.

These "forces of nature" include Gaia, Uranos, Chaos, the Fates, etc. who are ancient and primordial "gods" that are potentially more "powerful" than Zeus...even though he is the Lord of the Earth and Ruler of Olympus; also the River Gods have been shown to be sovereign from Zeus' rule, and the Fates themselves state that they serve a "greater goddess whose name is Necessity".

But even though Zeus is *not* the most powerful, what makes him "great" and "powerful" is how he wields what power he does have; in that respect, then yes: Zeus *is* one of the most powerful gods.

It should definitely be noted that his weaponry carried a great deal of that strength, being the terrific Thunderbolt that was crafted by the three Cyclopes for Zeus; this weapon did not exist until they created it for him in order to defeat the aforementioned Typhon, who had stripped Zeus of his tendons and imprisoned him in a cave...previous to that, he carried his father Cronus' sickle/scythe as his symbol of power but it was destroyed by Typhon during their fight.

With the Thunderbolt firmly in hand, Zeus silenced Typhon and took back the command of Earth and Olympus from him; the Thunderbolt has been his symbol of power ever since.