C is surprisingly efficient as well. Minimal keywords, terse syntax, single-character operators. Not much boilerplate, and the core logic is dense.
I think the worst languages are Java, C#, and Rust (lifetime annotations, verbose generics).
In my opinion, C or Go for imperative code, Factor / Forth if the model knows them well.
I cannot speak much for C#, but you may be right. Claude's Opus is really good.