I don't think Ronaldo has ever regretted joining Al Nassr they had enough good intentions so it was their choice, I know Ronaldo still failed this season because he couldn't bring any trophies and this club failed in all competitions but that doesn't mean Ronaldo has regrets because that and of course he has made a lot of contributions including to the team and also the fans are glancing at this SPL league.
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Even though he hasn't been able to provide a trophy for Al-Nassr, Ronaldo has been successful enough to prove that he is still productive in scoring goals. In 16 matches with Al-Nassr, Ronaldo managed to become #2 as the top scorer of the clubs under Talisca. he success with 14 goals, while Talisca with 20 goals. So, it is not impossible that next season with a full playing schedule, Ronaldo can give his first trophy for Al-Nassr. So far there has been no disciplinary action reported. This means that he has no regrets about his decision to play at Al-Nassr.
Ronaldo is almost always surprising at the start of his debut with his new team and with Al-Nassr he can still score so many goals, I think this GOAT has been thirsty for goals since leaving Manchester United. The first trophy for Ronaldo with Al-Nassr will still be open and it looks like he will keep trying until he gets it. In one of his interviews, Ronaldo said that he would still be playing football in the next 2 to 3 years and that did not rule out the possibility that after staying for several seasons with Al-Nassr he would simultaneously retire there.