Ethereum

Does this exist?

e.g send funds to A smart contract, smart contract anonymously sends to final B address (specified in "send to"). This simple, don't need anything else.

One Click Crypto. Any chain, any coin, any wallet → instant action. Grantee @ethereum, @optimism

crafting farcaster.in + terminal.co + @usetab // from cape verde 🇨🇻

ZkPay.finance for private payments. Natarouter.com for multichain privacy.

There were some pre last bull run.. But OFAC sanctions and pressure has got rid of (reduced liquidity for) most of them (because of laundering concerns). 

Mixers still exist though. Just a bit harder to find / use.

Onchain this hard as it would be quite easy to track specific amount that were send by one wallet and received by another (especially when its happening short period). Railgun/zkbob could potentially do what you want, maybe not in one click, but again it is tracable when using specific amounts and trying to do it fast.