  We present SKiLLS, a suite of multi-band image simulations for the weak
lensing analysis of the complete Kilo-Degree Survey (KiDS), dubbed KiDS-Legacy
analysis. The resulting catalogues enable joint shear and redshift calibration,
enhancing the realism and hence accuracy over previous efforts. To create a
large volume of simulated galaxies with faithful properties and to a sufficient
depth, we integrated cosmological simulations with high-quality imaging
observations. We also improved the realism of simulated images by allowing the
point spread function (PSF) to differ between CCD images, including stellar
density variations and varying noise levels between pointings. Using realistic
variable shear fields, we accounted for the impact of blended systems at
different redshifts. Although the overall correction is minor, we found a clear
redshift-bias correlation in the blending-only variable shear simulations,
indicating the non-trivial impact of this higher-order blending effect. We also
explored the impact of the PSF modelling errors and found a small yet
noticeable effect on the shear bias. Finally, we conducted a series of
sensitivity tests, including changing the input galaxy properties. We conclude
that our fiducial shape measurement algorithm, lensfit, is robust within the
requirements of lensing analyses with KiDS. As for future weak lensing surveys
with tighter requirements, we suggest further investments in understanding the
impact of blends at different redshifts, improving the PSF modelling algorithm
and developing the shape measurement method to be less sensitive to the galaxy
properties.
