The Strawhat Pirates (One Piece) are well known for their high bounties, but are even better known for their strengths in power. They are able to put together their physical and tactical abilities in order to pull off powerful team attacks that are capable of taking out stronger opponents.
Use a group's powers in combinations.
Team Combinations are techniques that are created by two or more people to take out a very powerful force or a large group that one cannot do alone.
This ability allows the user(s) to combine their strengths to form powerful alliances against common adversaries. For example, when someone with Electric Manipulation combines an attack with someone that used an attack with Water Manipulation. Not only do they do more damage than their attacks alone, but most likely be done at a bigger radius to take out more foes.
Superpowered Teams are not just for battle, some power combinations can save someone or some people for certain doom. An example would be when someone with Magnetism Manipulation and someone with Telekinesis lift a heavy metal object that neither could do alone to give people time to escape from harm's way.
Some team combinations are usually done by teams or crew, but they are more effective if the users practice enough.
Unfortunately, some combinations are ineffective against a certain being or fail to take out the whole army if the wrong power(s) are used.
Various characters (Dragon Ball series); via Fusion techniques
Guilds (Fairy Tail)
Various characters (Fairy Tail); via Unison Raid
Gundam Pilots (Gundam)
The 3-man Squads (Naruto)
A and B (Naruto)
Shinobi Alliance (Naruto)
Straw Hat Pirates (One Piece)
Precures (Precure Series)
Mizore Shirayuki and Kurumu Kurono (Rosario + Vampire)
Sailor Soldiers/Scouts (Sailor Moon)
Four Heavenly Kings (Toriko)
Ice Climbers (Ice Climbers)
Several characters (Kingdom Hearts)
Seekers of Truth (Person 4 and Golden)
Pokemon (Pokemon); via Water Pledge, Fire Pledge and/or Grass Pledge
Sonic and the Wisps (Sonic the Hedgehog series)
Teams (Sonic the Hedgehog series)
Sanger Zonvolt and Elzam von Branstein (Super Robot Wars); when piloting Dygenguard and Aussenseiter respectively
Jude, Milla, and their allies (Tales of Xillia)
Whenever The Mane Six (My Little Pony: Friendship is Magic) are together with their Elements of Harmony, they are able to combine their magic in order to banish or imprison anything that may prove as a threat to Equestria.
Steven Universe and Connie Maheswaran (Steven Universe) have been proven to make an excellent tag-team, Connie dealing offense and Steven defense.