Everyone knows Guitar George knows all the chords. If you don't believe me, just check him out.

But few know how he learned ALL the chords. I stumbled upon his bio and here is how he did it.

Guitar George studied the four primary chords (major, minor, diminished and
augmented) then built other complex chords such as 7th, 9th, 11th and 13th
chords. The trick is George did not try to memorize chords per se, instead
he committed formulae to memory for each chord type, and created the chord
needed using the appropriate formula. By understanding chord-construction
he was able to modify a chord, (make inversions). He practiced making minor
and major thirds on the keyboard then selected a note at random and counted
three half steps higher to make a minor third and four half steps higher to
make a major third. Actually, George built his advanced chords on the four
basic triad chords:
M3 + m3 = Major Triad
m3 + M3 = Minor Triad
m3 + m3 = Diminished Triad
M3 + M3 = Augmented Triad


That said, Guitar George was not "complete" since he has been repeatedly
described as "strictly rhythm" and he wasn't technologically superior (he
could only afford an old guitar).