The Grenadier is an infantry unit able to use indirect fire to attack the second or third row on the battlefield, even if blocked by a blocking unit in front of it. In addition, they deal Explosive damage. Grenadiers, however, suffer from limited ammo capacity and long reload times once their ammo is expended, and while being fairly fragile unit, making them extremely vulnerable when they are out of ammo.
In early levels from when Riot Troopers appear until Mini Tanks become available, the Grenadier is the ideal unit to handle armored units, like the Riot Troopers.
Once upgraded, Flashbangs can be issued to the Grenadiers after conducting the research to unlock it. The Flashbang attack causes minimal damage, but in turn causes 100% stun effect to the target, with a reduced chance to affect units adjacent to the target. Its unlocking of a second ability slot coincides with the unlocking of the Flashbang attack, thereby allowing the Grenadier to equip both the basic grenade attack as well as Flashbang, giving this unit much greater flexibility.
It's third attack, the Incendiary Grenade, becomes available at Rank 3. Although this attack does not do as much instant damage as the Small Grenade, it will do more damage overall due to its damage-over-time component. This attack's usefulness is offset by its rather lengthy three-turn cooldown.
A fourth attack, Handful of Grenade, becomes available at Rank 4. The Grenadier will make 3 separate attacks at the selected center space, with a chance the grenades will deviate towards one of the adjacent spaces. This attack's ammo cost makes the Grenadier a one-trick pony, however the player could potentially do 150+ damage on a single target at Rank 5, which is a massive amount at low levels, and a moderate amount at higher levels.
With so many different attack options that can be unlocked, and with two ability slots to mix-and-match them, the Grenadier proves a quite useful and versatile unit at early levels.