What are the worst things the Imperial Guard have ever done?
I feel like despite being the militant arm of the bloodiest regime imaginable, Guardsmen are often portrayed in the narrative and the collective conscience as victims of the Imperium, sent to fight and die in untold billions in hopeless battles.
So, what are the worst atrocities that were ordered and carried out by boots-on-the-ground guardsmen?
To clarify, I'm not really talking about 'They were sent to quell rebellion on this peacefully protesting planet', because Guardsmen don't generally get a choice in what and where they're deployed to fight. More interested in the smaller, unnecessary moments in which they demonstrate that they are, after all, sons of the Imperium.