You can only activate "Big Burn" when an EFFECT that removes monsters in the Graveyard is activated. So you can't activate "Big Burn" when a player removes monsters in the Graveyard as a COST to Special Summon "Black Luster Soldier - Envoy of the Beginning", "Chaos Emperor Dragon - Envoy of the End", or to activate the effect of "Strike Ninja" or "Freed the Brave Wanderer". Nor can you use "Big Burn" when monsters are removed for a condition.

"Big Burn"s effect is negated if "Necrovalley" is active.The latest print of "Necrovalley" has Problem-Solving Card Text which states that it prevents cards in the Graveyard from being banished, so effects that banish cards from the Graveyard are not negated, but rather cannot banish any cards from the Graveyard.

You can chain "Big Burn" to effects like "Disappear", "The Shallow Grave", or "Spear Cretin".

You can't activate "Big Burn" when "Sinister Serpent" activates in the Graveyard, because "Sinister Serpent" doesn't target.

When "Spirit Elimination" is activated and "Big Burn" is chained, the player who activated "Spirit Elimination" removes all monsters on his side of the field. The other player removes all monsters in the Graveyard as usual.

Amplifier"Jinzo with Amplifier", your Trap Cards are not negated and their effects are applied, including "Big Burn".

Exchange of the Spirit: "Exchange of the Spirit" does not target cards in the Graveyard, so "Big Burn" cannot be activated.

Necrovalley: "Necrovalley" negates effects that require removing cards from the Graveyard. "Necrovalley" WILL negate card effects like "Big Burn"

The End of Anubis: "The End of Anubis" WILL NOT negate the effect of "Fiend Comedian", "Fiber Jar", or "Big Burn".