Illinois under Brad Underwood:
NCAA Tournament Year - Finish
2018 - No tournament
2019 - No tournament
2020 - COVID
2021 - 1 - Round of 32
2022 - 4 - Round of 32
2023 - 9 - Round of 64
2024 - 3 - Elite Eight
If you use this and expected number of wins from when we made the tournament:
https://bracketodds.cs.illinois.edu/seedadv.html (thanks whomever did this)
2021 - 1 seed - 3.30 wins
2022 - 4 seed - 1.56 wins
2023 - 9 seed - .62 wins
2024 - 3 seed - 1.84 wins
I believe that's 7.32 wins expected in 4 tournaments and his actual is 5 wins (Rd 32 {1 win}, Rd 32 {1 win}, Rd 64 {0 wins}, Elite Eight {3 wins}). So even ignoring what he inherited and the first 3 years of his tenure, I don't think it's unreasonable to think he's underachieved in the NCAA tournament.
FWIW, I like old fiery Brad and what he's done to turn the program around is amazing. But I don't see the fire in him on the sideline and there are times where his stubbornness and resistance to in-game adjustments absolutely hurts the team.