The AMD Ryzen 7 3800X managed to achieve an impressive 5.9 GHz single-core overclock on LN2. Pro-overclocker 'TSAIK' achieved this on an MSI MEG X570 GODLIKE motherboard and also managed to overclock the DDR4 RAM up to 5,774 MHz. There are no performance numbers yet, but it looks like the Ryzen 7 3800X has very good overclocking potential.
https://www.notebookcheck.net/AMD-Ryzen-7-3800X-pushed-to-5-9-GHz-along-with-DDR4-RAM-at-5-774-MHz-on-LN2-seems-to-have-good-potential-for-an-all-core-overclock-record.427697.0.html