Number 2: Skullclamp Although it may look innocuous, veteran players will recognize this card for the powerhouse it really is

Bumbleflower Rank #12 3,647decks Tony Stark Rank #13 3,409decks Atraxa, Praetors' Voice Rank #14 3,408decks Toph, the First Metalbender Rank #15 3,391decks Krenko, Mob Boss Rank #16 3,381decks Lathril, Blade of the Elves Rank #17 3,239decks Chatterfang, Squirrel General Rank #18 3,229decks The Unbeatable Squirrel Girl Rank #19 3,065decks Kaalia of the Vast Rank #20 3,007decks The Wise Mothman Rank #21 2,983decks Ashling, the Limitless Rank #22 2,970decks Sephiroth, Fabled SOLDIER Rank #23 2,938decks Kefka, Court Mage Rank #24 2,935decks Frodo, Adventurous Hobbit // Sam, Loyal Attendant Rank #25 2,918decks Giada, Font of Hope Rank #26 2,852decks Bruce Banner Rank #27 2,762decks Hakbal of the Surging Soul Rank #28 2,611decks Captain America, Team Leader Rank #29 2,611decks Jodah, the Unifier Rank #30 2,555decks Witherbloom, the Balancer Rank #31 2,528decks Norman Osborn Rank #32 2,527decks Isshin, Two Heavens as One Rank #33 2,488decks Rin and Seri, Inseparable Rank #34 2,463decks Bello, Bard of the Brambles Rank #35 2,427decks Valgavoth, Harrower of Souls Rank #36 2,388decks Nekusar, the Mindrazer Rank #37 2,380decks Terra, Herald of Hope Rank #38 2,379decks Tidus, Yuna's Guardian Rank #39 2,350decks Blech, Loafing Pest Rank #40 2,320decks Nick Fury, Agent of S.H.I.E.L.D

Even so, theres probably an insufficient critical mass of payoffs and wincons for these strategies if they keep killing your Nekusar, for example
Any abilities that trigger won't be put onto the stack until Mystic Confluence is done resolving
That sacrifice causes the ability of the other player's Grave Pact to trigger, and so on