Raddysh emerged as one of the top offensive defensemen in the NHL during the 2025-26 season. His 22 goals and 48 assiss were NHL career highs and he set a Tampa Bay Lightning record for most goals by a defenseman. He also scored 10 power-play goals to lead NHL defensemen and became the second Lightning skater at his position with a 70-point season, joining Victor Hedman (three times).

Raddysh's 2024-25 season was the first of a two-year contract he signed with the  Lightning on Aug. 23, 2023. The undrafted defenseman had 31 assists and 37 points in 73 games to help the Lightning reach the Stanley Cup Playoffs. His six goals tied Nick Perbix for second most among Tampa Bay defensemen behind Hedman (15). Per NHL EDGE, he had 40 shots that reached at least 90 miles per hour, tied for fifth most among all skaters.

Raddysh played 82 games for the first time in the League in 2023-24 (33 points; six goals, 27 assists). He played 17 games with the Lightning in 2022-23 once he joined them from Syracuse in the American Hockey League on March 2 and debuting that night against the Pittsburgh Penguins. His 51 points in 50 games for the Crunch was tied for third among AHL defensemen and he averaged 23:13 of ice time in the 2023 NHL playoffs, second on Tampa Bay behind Mikhail Sergachev (26:55).