Could you wish for an ability score of 30 in D&D?
Wish states (after some examples that seem less powerful than what you're asking):
You might be able to achieve something beyond the scope of the above examples. State your wish to the DM as precisely as possible. The DM has great latitude in ruling what occurs in such an instance, the greater the wish, the greater the likelihood that something goes wrong. This spell might simply fail, the effect you desire might only be partly achieved, or you might suffer some unforeseen consequence as a result of how you worded the wish. For example, wishing that a villain were dead might propel you forward in time to a period when that villain is no longer alive, effectively removing you from the game. Similarly, wishing for a legendary magic item or artifact might instantly transport you to the presence of the item's current owner.
In other words: yes you can try, but it's up to the DM to decide what exactly happens. Considering this would be an pretty powerful wish, you might not like the unforeseen consequences. I wouldn't try it. Before you know it you're transformed into a Kraken.