What's the best way to swap $800k BTC to USDT?

I’m looking for the best and safest way to swap around $800k worth of BTC to USDT.

Most big exchanges either have strict limits or require full verification for this amount, and I’d prefer something smooth and reliable. I don’t mind using P2P, an OTC desk, or a trusted platform. I just want to avoid unnecessary delays or frozen funds, I CAN'T LOOSE THESE FUNDS.

Has anyone here done a large swap like this recently? Would really appreciate hearing what worked for you, what the process was like, and if there’s anything important to watch out for.

Thanks in advance for any advice or recommendations.