A simple LoRA that increases breast size, strength should be between 0.3-0.7 (depends on model, start with 0.5 and experiment)

Can also enhance normal "big/large/huge breasts" inside the prompt in addition to increased word weighting.

Tested it with some 2d, 2.5d and 3d/realistic models and seems to work well with everything I throw at it. See examples. (but it's not perfect, especially with higher strength and realistic models it tends to over tune)