Óðinn

Odin is the god who pays for what he knows. Twice the sources show him buying knowledge with his own body: he leaves an eye in Mímir's well for a single drink from it, and in Hávamál he hangs nine nights on a windswept tree, wounded with a spear, given to himself, until the runes come to him and he falls back screaming. Neither trade makes him safe. What he buys is knowledge, and the knowledge he gathers includes how the world ends and how he dies in it. It does not let him escape.
That pattern runs through everything else. He is the god of poetry because he stole the mead of poetry from the giants in the shape of an eagle; the god of the dead because he needs an army for a battle he already knows he loses; the god of wisdom because he keeps asking, of seeresses, of severed heads, of anyone who will answer. His ravens Huginn and Muninn fly out each day so that he misses nothing, and Grímnismál has him admit he fears more for Muninn, memory, than for Huginn, thought.
He is also, plainly, not trustworthy. Hávamál says he swore an oath on a ring and then cheated the giant Suttungr, and asks who could trust his word. He gives victory and then withdraws it, because the warrior he abandons is the warrior he gains. Lokasenna throws his practice of seiðr at him as unmanly, and the poem lets the accusation stand. The sources are not embarrassed by any of this: a god of frenzy, poetry and the gallows is not supposed to be safe.
His name says as much. Old Norse Óðinn is built on óðr, the word for fury, inspiration and poetry, so the name means something like 'master of frenzy'. Behind it stands Proto-Germanic *Wōðanaz, which gives Old English Wōden and, through him, Wednesday. Tacitus, writing around 98 AD, says the Germani worship 'Mercury' above all other gods, and that is generally read as this same figure, more than a thousand years before anyone wrote the Eddas down.