This may sound silly, but when I first replaced a tie rod end on our 2002 Bonneville I attempted to loosen it by gripping the tie rod with one wrench and what I thought was a six sided portion of the tie rod end with another wrench, not realizing that I was just tightening the tie rod end.
The "six sided portion of the tie rod end" is actually just a nut that was used for locking the tie rod end in place. It looked so well formed to the tie rod end that I couldn't tell the difference. If this is also your problem, the best way to remove it is to grip the tie rod end, there'* a flat spot a wrench can grip near the ball, and loosen the nut away from it first. The tie rod end should unscrew easily after that.