Ward Beullens
Belgian cryptographer whose 2022 paper "Breaking Rainbow Takes a Weekend on a Laptop" did exactly what the title promised.
Rainbow, Jintai Ding's layered variant of Oil and Vinegar, was a finalist in NIST's post-quantum competition, with small signatures and fast verification. In February 2022 Beullens, then at IBM Research Zurich, published a new attack that recovered the secret key for the lowest security level in a little over two days on a laptop. Rainbow was not selected.
He had already eaten into Rainbow's security margin in 2021; plain UOV, the simpler scheme underneath, was not affected in the same way. His own proposal, MAYO (2021), is a UOV variant with much smaller public keys and went on to NIST's additional round for signatures. Break other people's schemes for long enough and eventually you have to put one up yourself.