heavy hitter

Short definition from Wiktionary

Noun

1. 1
   A player with a favorable batting average who is especially good at hitting the ball deep into the outfield or farther.
2. 2
   In any sport, a strong, physical player who is particularly effective.
3. 3
   A person of considerable importance who is a major decision maker or capable achiever; an especially significant organization or an especially functional object.
4. 4
   Alternative form of heavy hitter.