So the term grenadier originally referred to soldiers who throw grenades. They were physically larger, stronger, specially trained troops meant for hurling grenades at the enemy.
Eventually the European powers worked out this was a bad idea and by the Napoleonic wars grenadiers just meant elite troops.
But there was a long time when you did have these large bodies of troops trained to chuck grenades at each other. Were there any large battles where this was an major factor and decided who won the battle?
I’m unable to find an example of grenadiers (in the sense of specialized bomb throwing infantry) actually being crucial to winning a battle. There are probably many ship to ship battles that qualify (especially in the age of Greek fire) but I doubt that was a specialist class like it was in armies.
The original role of grenadiers was to lead the assault on fortified positions, throwing their grenades amongst the defending troops. As such they were more an added force rather than a battle-winning one. Later in their existence, they continued to lead the assault minus their grenades.
They didn’t stop using them to chuck explodey things at the enemy because it was a bad idea. They stopped using them because of improvements in both weapons and tactics, and because they found that it was better to include grenade chuckers in with elite fast assault forces than to have them as separate units.
This implies that you had a group of big hefty dudes tossing grenades at the enemy group of big hefty dudes. While Grenadiers were initially in separate units and remained that way for some time, they didn’t typically fight this way (a unit of Grenadiers fighting an enemy unit of Grenadiers with no one else involved). They were usually sent into battle alongside infantry units. For example, if you wanted to do a flanking maneuver, you might send two units of fast infantry along with one unit of Grenadiers. You wouldn’t just send the Grenadiers alone.
I don’t know of any large battles were credit for the win went exclusively to Grenadiers, but they were extremely effective on the battlefield. For example, when the French first used Grenadiers against the Dutch, the Dutch immediately decided that they needed Grenadier units of their own, and the use of Grenadiers then very quickly spread throughout all of Europe.
A similar thing happened in India. The Sepoys sent two units of Grenadiers into battle alongside several units of infantry, and found the Grenadiers to be so effective on the battlefield that the Sepoy Army immediately ordered an entire battalion of Grenadiers to be created.