#1 He could have won a World Cup by now
The only trophy that Messi must regret not winning in his storied career is the World Cup. He has even admitted that he would give up all his individual honours just to win the trophy once. And he came painfully close at the 2014 World Cup before losing in the final to Germany. But interestingly, he could have won a World Cup by now if he had just taken a different decision as a youth.
Messi moved to Spain as a 13-year-old and is very much seen as Barcelona's own. As a result, he was offered a chance to play for the Spain national team. But he rejected the offer as he wanted to achieve international success for his beloved Argentina.
As we all know, Spain won the World Cup in 2010, while Messi is yet to lift any international trophy with Argentina.