#2 Sevilla
After finishing third in the UEFA Champions League group stage, Sevilla was transferred to the UEFA Europa League. Sevilla completed their hat-trick of UEFA Europa league title with a 3-1 victory over Liverpool in 2016 final. Coke scored a brace and Gamerio was the other goalscorer for Sevilla. This was their 5th UEFA Europa League title, and Sevilla is the most successful club in UEFA Europa League history.
In the 2015-16 season, Sevilla finished 7th in La Liga and lost to Barcelona in the Copa Del Ray final. Kevin Gamerio scored 24 goals across all competitions and was the top scorer for the club.
#1 Atletico Madrid
Atletico Madrid won their third UEFA Europa League title in 2018 when they defeated Marseille by 3-0 in the final. Antonio Greizmann scored a brace and Gabi was the other goalscorer for them. This was their 3rd UEFA Europa League title. Atletico Madrid failed to qualify for the knock out round of UEFA Champions League, and due to their third-place finish in the group, they were shifted to UEFA Europa League.
In the 2017-18 season, they finished 2nd in La Liga and reached the quarterfinals of Copa Del Ray. Antonio Griezmann was their top scorer with 29 goals across all competitions.
Sources:-
https://us.soccerway.com/international/europe/uefa-cup/
https://us.soccerway.com/international/europe/uefa-cup/
https://www.uefa.com/uefaeuropaleague/history/