Low concentration spreads dark matter too broadly. Diffuse core produces a shallow potential well — the rotation curve rises slowly and peaks weakly at 165 km/s before flattening far out at 12 kpc. The galaxy lacks central density; inner stellar orbits are underpowered.
The Goldilocks concentration. NFW profile at c=10 matches observed Milky Way–type galaxies perfectly. The halo provides the right potential depth — rotation curve rises smoothly to 210 km/s, flattens naturally at 8 kpc, and sustains a realistic spiral structure with well-defined arms and central bulge.
Over-concentrated dark matter creates a cuspy inner rise — the rotation curve spikes sharply to 255 km/s then drops, flattening too early at just 4 kpc. The excessive central density disrupts disk formation, compressing gas violently and distorting stellar orbits in the inner region.