According to the Center for Responsive Politics, of the ten most expensive House races in 2020 (i.e., the races with the most money spent by candidates, not including spending by outside groups), two candidates won their races despite being outspent by their opponents.
Democratic Rep. Ilhan Omar spent $5.2 million. Her Republican opponent, Lacy Johnson, spent $9.7 million. Omar won her bid for reelection in Minnesota's 5th Congressional District.
Republican Troy Nehls won his race in Texas's 22nd Congressional District against Democratic opponent Sri Kulkarni. Nehls spent $1.4 million and Kulkarni spent $4.2 million.