"I want to be able to do one pull-up."
This is a common goal I get from people doing my online and in-person training, especially with females.
Being able to do pull-ups is an excellent measure of upper body strength. I've heard it framed before that pull-ups are for your upper body what squats are for your lower body. Maybe, maybe not, but one thing is for sure is that pull-ups are much more difficult to improve.
Pull-ups have been linked from everything to greater athleticism and improved 40 yard dash times. And in my observation this is true. Some of the greatest athletes I've worked with, even those over 240 pounds, can do multiple pull-ups.
Check out this article from stack.com called Do Your First Pull-Up . It gives you an 8-week guide on how to either get your first one done or increase the number of pull-ups you already do.
You'll notice there isn't any mention of band assisted pull-ups. This is something I've been slowly starting to hate. Reason being is that all of your assistance is at the bottom of the movement. However, the most challenging part is the top portion. The band gives you nothing at the top because of its variable resistance.
The argument is, the bands will help me improve the number of repetitions I can do, my non-assisted pull-ups will improve. I'm not sold on this. If your goal is only doing repetitions of band assisted pull-ups, I think it's okay. But, if your goal is to be able to do an unassisted pull-up, it's not the route to take.
Negatives, jumping pull-ups (slowly taking away the velocity of the jump), anti-extension core work, upper body pulling, partner assisted pull-ups, and losing body weight are better choices.