When Fiend Hunter enters, its first ability triggers, exiling Karmic Guide.
Activate Goblin Bombardment by sacrificing Fiend Hunter.
When Fiend Hunter dies, its second ability triggers, returning Karmic Guide from exile to the battlefield.
When Karmic Guide enters, it triggers, returning Fiend Hunter from your graveyard to the battlefield.
When Fiend Hunter enters, its first ability triggers, exiling Karmic Guide.
Resolve the Goblin Bombardment ability.
Repeat from step 3.
This resilient loop spins into an infinite execution machine by catching Karmic Guide in a continuous cycle of exile and resurrection. When Fiend Hunter enters the battlefield to permanently stow away Karmic Guide, it sets the stage for Goblin Bombardment to effortlessly sacrifice the Hunter, triggering its leave-the-battlefield effect to release Karmic Guide right back to the fray. That new entry triggers Karmic Guide's ability to drag Fiend Hunter straight out of your graveyard, restarting the sequence and letting Goblin Bombardment pepper any target with infinite damage.