Nobody is quite like Banks.

Some of the closest would likely be:

Charles Stross' various SF, especially the space opera-adjacent stuff. (He has an large range. Merchant Princes and Laundry series are good, but not at all along the lines of Banks.)

Gregory Benford's Galactic Center Saga.

Vernor Vinge's three Zones of Though books.

David Brin's Uplift series.

Perhaps Hannu Rajaniemi's Jean le Flambeur series.

Max Gladstone's Emperess of Forever shares a similar setting, but is much lighter.

The writing of Gene Wolfe and Tamayn Muir has, I think, much in common with Banks in terms of depth and character, but even though SF they have a very different feel and focus to their works.

And, of course, if you want the original space opera, it might be worth tracking down E.E. "Doc" Smith's Lensmen books. Galactic Patrol and Grey Lensman are the heart of it and ought to be read first. Second Stage Lensman and Children of the Lens are worthy sequels that complete the story. They're pretty breezy reads and very different from Banks in everything but the setting of a galaxy filled with different species, and likely seem somewhat hackneyed now, but they're also the source of most space opera archetypes. (If you think of a space opera trope, it probably came from Lensman. Star Wars is largely a Lensman/Flash Gordon mashup.)