Real Betis should really not be underestimated, but based on the odds, they should be. Chelsea are really prepared for the match, and Real Betis also are.
The finals will literally be complicated because of the fact that Real Betis's manager understands Premier League clubs, but based on the odds, they say the trophy is for Chelsea.
How brilliantly Chelsea played their last match shows that they are very much ready for real betis but we’ll wait for the final whistle to see who will really get the trophy.
Make your decision mate. Should they be underestimated or not?

Chelsea are really highly favoured for the trophy. There is nothing wrong with that considering the quality difference between 2 teams.
There is only one handicap for Chelsea here. They played a Champions League decider match in the Premier League 2 days ago. The fatigue will be their biggest enemy. If they deal with it well then I don't think there will be a surprising result.