When the time comes for Thanos to wield the completed Infinity Gauntlet in the Marvel Cinematic Universe, the might of the Avengers simply won't be anywhere near enough to stop him.
Add in the Guardians of the Galaxy and even that won't be enough to prevent the Mad Titan from causing universe-altering destruction with his godlike powers.
Then take into account that Thanos probably won't be working alone and you'll come to realise that it's going to take a huge joint effort from a number of teams, groups and organisations to combat the big-bad of the franchise.
This article will take a look at the different parties that could come together to fight for the same cause over the course of the two Infinity War movies (in 2018 and 2019 respectively) – and indeed in the spin-off media like the television shows – to go up against Thanos. It will also emphasise the potential scale of that battle.
S.H.I.E.L.D. are still a presence in the Marvel Cinematic Universe – as proven when the Helicarrier appeared at the end of Avengers: Age of Ultron to aid the titular heroes in their fight against the robotic villain – and they will undoubtedly be involved in the battle against Thanos.
Whether any agents appear in the movies or whether they'll be restricted to television roles, they'll certainly be impacted by the Mad Titan's actions – as will the entire universe – and they will undoubtedly act in some way.
Phil Coulson is currently in the process or rebuilding the organisation after it was parasitically infiltrated by HYDRA, but as they continue to grow they will become a more valued asset in the good fight in the MCU.
They may provide backup during the actual battle against the villain or they may simply provide reconnaissance in the same way they did with Loki's sceptre, but they will definitely be involved in some way.