Absolute incudes Halion (and all that is included in Halion). It’s all on Steinberg’s site if you do a little digging.
Click Cubase 10 Pro and Virtual Instruments on this page to see the vsti’s in Cubase: https://new.steinberg.net/cubase/features/
Scroll down about half way on this page to see what’s included with Absolute: Absolute: VST Instrument Collection | Steinberg
And scroll down about 1/3 on this page to see what’s in Halion: https://www.steinberg.net/en/products/vst/halion_and_halion_sonic/instruments_and_effects.html
I would imagine that to get all the content that Steinberg offers,
you’d have to buy everything currently available for purchase on their site, after sorting out duplicates.
I have several versions of Cubase and Absolute and that’s more than enough for me.