The glute-ham machine is one of the best exercises for hamstring size and strength. You can also do the “natural” version kneeling on a mat with your feet anchored down. The challenge with this version is that the leverage is much harder.
Many strong lifters can’t even do one Nordic leg curl. Many have to do eccentric (lowering-only) reps. This can work, but doing eccentric reps with more than your one-rep max will get you very sore and can delay recovery.
By adding band assistance, you can start at your current strength level. Bands are perfect because they provide the most help at the bottom (where you need it the most) and the least help at the top (where you don’t need it).
Regression: Use more bands, thicker bands, or a higher anchor point.
Progress: Use fewer bands, thinner bands, or move the anchor point lower.