That would depend on several factors, including hash rate, power consumption, and cost. Some of the most cost-efficient ones are in my opinion the Antminer S19 Pro (110 TH/s at 3250 watts), T19 (84TH/s at 3150 watts), or the Whatsminer M30S++ (112 TH/s at 3400 watts).

The profitability of mining depends on various factors, such as BTC price, the difficulty of mining, and the cost of electricity. So it's crucial to do your own research and consider all factors before investing in a mining machine.

To estimate the expected ROI, you can use the various calculators found online such as https://www.asicminervalue.com/