Before playing at Florida State University, Bethune was a three-year contributor at the University of Central Florida. From 2019-21, he recorded 185 tackles (13 for loss), 4.5 sacks, three interceptions and two forced fumbles in 35 games (17 starts). Bethune led the Knights with 101 tackles during the 2021 season, becoming the 43rd member of UCF's 100-tackle club. He also earned an All-AAC honorable mention by the league's coaches, was named to the second-team All-AAC by Pro Football Focus and second-team All-AAC by Phil Steele that year.
The linebacker later transferred to FSU for his final two seasons of college football. From 2022-23, Bethune made 24 game appearances with 21 starts and recorded 142 total tackles (12.5 tackles for loss), 1.0 sack, one interception, seven passes defended and one fumble recovery.