Complex sentence: Of the two, Goofather was always the strong developer, while BillyEvil had his strengths in testing and selling new ideas to people, together they made a great team as they complemented each other's weaknesses and strengths.
Split into simpler sentences: Of the two, Goofather was always the strong developer, while BillyEvil had his strengths in testing and selling new ideas to people. Together they made a great team as they complemented each other's weaknesses and strengths.