That answer is a little more complicated, since a large majority of deck lists that youll find in other places are extremely outdated and/or untested
As for the effect, it was evaluated at the time that it was a very plain effect with a canosol that has a limit on the number of times and attacks, but the damage is 1000, which is unexpectedly ridiculous
If you want the Mewtwo V SA specifically, buying the single at ~$85120 is far cheaper than chasing through boxes (estimated ~25 boxes for a specific SA pull)
However, Dark Hole forced players to destroy their own Monsters (or play it on an empty field), and Lightning Vortex required a player to discard a card in their hand to activate it, making Raigeki the easy include over both when it was finally brought back to the game
C Common Sun Dragon Inti X LIGHT Level 8 [ DragonSynchroEffect ] ATK 3000 DEF 2800 "Fire Ant Ascator" + 1+ non-Tuner monsters If this card is destroyed by battle and sent to the GY: Destroy the monster that destroyed this card, and if you do, inflict damage to your opponent equal to half the ATK that monster had on the field
Two Keywords Having just two keywords is fine if theyre awesome enough, and I think all of these definitely make the grade, even Jewel Thief, which can help you ramp mana with a Treasure token if you need to deploy it to the battlefield first