As the title reads, it seems very confusing what actually kills a Transformer.
Case 1: Jazz is ripped apart by Megatron in Transformers
Case 2: Megatron is killed by the AllSpark in Transformers
Case 3: Megatron is brought back to life by the AllSpark shard and given parts by a Decepticon Transformers 2: Revenge of the Fallen
Case 4: Optimus Prime is killed by Megatron in Transformers 2: Revenge of the Fallen
Case 5: Optimus Prime is brought back to life by Sam Witwicky by fusion of the Matrix of Leadership in Transformers 2: Revenge of the Fallen
Case 6: Optimus Prime rips The Fallen's Spark out in Transformers 2: Revenge of The Fallen
Case 7: Megatron is killed by Optimus Prime in Transformers 3: Dark of the Moon
Case 8: Ironhide is killed by Sentinel Prime in Transformers 3: Dark of the Moon
Case 9: Optimus Prime has a shell lodged in his chest area and remains dormant for years until Cade Yeager dislodges it in Transformers 4: Age of Extinction
Case 10: Ratchet is killed by Lockdown in Transformers 4: Age of Extinction.
Case 11: Megatron is infused into a new Transformer shell by Joshua Joyce as a new Transformer Galvatron in Transformers 4: Age of Extinction
As you can see from the cases above, some remain dead, others are given life by the AllSpark/Matrix of Leadership or are simply rebuilt.
So the question stands, do Transformers actually die, given that some Transformers remain dead and others are brought back to life?
Antimatter Bomb
... AFAIK, they are made up of matter!