Send the real stuff and Russia loses. Exportable F16 Vipers, older Abrams tanks which are better than what Russia has, older Apache tank killers.
Problem is, the Ukrainians would have to train on them, and they would need the right ammo and spare parts. OK. So send them what they can use right now and plenty of them, but on lend-lease terms. Their chain of command is better, their motivation is better, and their doctrine is more flexible. They don’t need state of the art, but they need something to end this quickly.