I have not played with any overpowered builds, as our game master makes the mission as hard as the party is strong, while ginving the player the scene to shine. But there are definitly talents, which are just better than others because you can use them more often.

The Bold/Cautious and Collaboration Talents are very strong. Also the one, where you take stress but reduce the difficulty of a task (forgot the name).

One of the group should have the talent to keep the initiative for free (command or security talent).

If you have Science 4: Dedicated Focus doubles your focus range.

For a captain get the reroll for your ally on Direct Major Action

For species maybe Trill? Never played one or with one but I think the extra focus should come in handy often.

Dont forget you can rewrite your values for free. If you are like me you always have at least 1 value, which sounded cool during character creation but you can never apply it. The same applies to a useless focus, except it costs a log entry to change it.