Complex sentence: In 2007 he defeated Tomasz Adamek to win the WBC title, and after vacating that title defeated Antonio Tarver in 2008 to become the IBF and IBO champion.
Split into simpler sentences: In 2007 he defeated Tomasz Adamek to win the WBC title. After vacating that title, Dawson defeated Antonio Tarver in 2008 to become the IBF and IBO champion.