Here's my method.
C Clamp
10mm axle spacer (or similar)

Note this cotter is already pushed, but I wasn't going to drive it back in just for a picture.

For a day or 2 before removal, apply a couple drops of penetrating oil and let it soak. repeat frequently.
Having the treads "up" and nut removed helps.
Screw nut back on so that threads are "flush".
I use the "solid" part of the C clamp here.
Use the 10mm spacer on the opposite side as a "receiver".
The "swivel" side of the C clamp seems to be a bit more "solid" on this side.



The finer the threads on the C clamp, the greater the force applied. Some C clamps have relative coarse threads.