1 Tuner + 1 or more non-Tuner monsters Once per turn: You can target 1 card you control and 1 card your opponent controls; destroy them. When this card is destroyed by your opponent's card (either by battle or by card effect) and sent to the Graveyard: Target 1 non-Synchro "Scrap" monster in your Graveyard; Special Summon that target.
Removal effect requires you to also destroy one of your cards.
Scrap monsters like to destroy themselves to trigger their effects so Scrap Dragon’s removal effect can gain you even more advantage. Additionally, a good way of summoning Scrap Dragon is by using Scrap Golem to revive Scrap Goblin.
Nephthys is another archetype that like to have their monsters destroyed with an effect. Most prominently Sacred Phoenix of Nephthys is able to revive itself and clear all Spell/Trap cards on the field after it was destroyed via a card effect.
Activate Widespread Dud and select 2 of your opponent’s monsters. Use Scrap Dragon’s effect to destroy an opponent’s monster and Widespread Dud, which will cause Widespread Dud to destroy the 2 other selected monsters resulting in a monster zone wipe.
Activates from your Graveyard
Destroys your Monster Cards / Destroys your Spell Cards / Destroys your Trap Cards / Destroys your opponent's Monster Cards / Destroys your opponent's Spell Cards / Destroys your opponent's Trap Cards