Optimus

- He died while protecting you from Megatron

Ratchet

- He died in an accident while he was taking you to the hospital while in his alt mode

Bumblebee

- He died while protecting you from scraplets when they attacked you because of your necklace

Arcee

- She died while she was saving you from a fire

Smokescreen

- He died after saving you from drowning

Bulkhead

- He died after he saved you from the government

Wheeljack

- He died while saving you from an insecticon
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Nightpoppy gave me the idea for the 'how they died for you' chapters