If Sephiroth, Fabled SOLDIER and one or more other creatures die at the same time, its last ability will trigger for each of those other creatures
Shinryu has high attack and flying, making eliminating a player with commander damage a serious possibility
If you just want a clean, straightforward one-turn kill, Chandra's Ignition is a pretty good option, able to smite every creature and player in such dramatic fashion that they probably won't really mind
3 Chaos, the Endless Clive, Ifrit's Dominant Cloud, Planet's Champion Esper Terra Firion, Wild Rose Warrior Freya Crescent Garland, Knight of Cornelia Gilgamesh, Master-at-Arms Giott, King of the Dwarves Gladiolus Amicitia Ifrit, Warden of Inferno Joshua, Phoenix's Dominant Kefka, Court Mage Kefka, Ruler of Ruin Kuja, Genome Sorcerer Lightning, Army of One Lightning, Security Sergeant Phoenix, Warden of Fire Prompto Argentum Queen Brahne Raubahn, Bull of Ala Mhigo Rydia, Summoner of Mist Seifer Almasy Shantotto, Tactician Magician Tellah, Great Sage Terra, Magical Adept The Emperor of Palamecia The Fire Crystal The Lord Master of Hell Trance Kuja, Fate Defied Vaan, Street Thief Vivi Ornitier World Champion, Celestial Weapon Zell Dincht Zidane, Tantalus Thief
Graded Population Report: Jumbo Cactuar #191 Visualize the distrbution of grades in the chart
It doesn't copy any information about the object the card may have been at any point before it was exiled
