2000 ford f150 ABS activates every brake?

Everytime I brake gradually abs engages around 10mph to stop. Unnerving with slippery weather coming up. No codes are thrown. It pulls right so has to be a front left abs sensor correct?

Don't guess which sensor. Get a scanner with wheel speed data and watch as you drive. You may find it has a cracked tone ring at one of the hubs, a very common problem with Ford. If you are able to pull the wheels and get a look at the rings you should be able to see it.

Nope. Your ABS system should be dropping out at that speed not activating. First off disconnect one of the sensors, that will deactivate the ABS system and do a road test to be sure it is not something with the brake system. If it stops try to reboot the ABS computer by unplugging it.

Usual suspects are metal flakes on the face of the sensor or excessive rust buildup on the tone ring teeth. Wire brush the tone rings with a brass bristle brush. Then clean the metal particles off the tone ring and the face of the sensors on both sides and try again.

Or a seized piston in the right caliper

Check that there's no dirt on the sensor rings and the sensors are in position correctly.
Are you sure it is the ABS? Silly question you should also check the pads when you have the wheels off to check the sensor rings and sensors.