Alongside being powerful and effectively free removal, Solitude will be an absolute menace in blink-heavy decks like Yorion, Brago or Roon, where you can easily repeat its enter-the-battlefield effect to keep removing creatures as much as you need
Not too bad, but four mana for one card is a tad high

Creature Legendary Olivia, Opulent Outlaw Vihaan, Goldwaker Massacre Girl Fain, the Broker Kamber, the Plunderer Mari, the Killing Quill Rankle, Master of Pranks Captain Lannery Storm Grenzo, Havoc Raiser Laurine, the Diversion Breena, the Demagogue Queen Marchesa Non-legendary Angelic Sell-Sword Witch of the Moors Nighthawk Scavenger Misfortune Teller Ogre Slumlord Charred Graverobber Marshland Bloodcaster Veinwitch Coven Dire Fleet Ravager Mirror Entity Dire Fleet Daredevil Angrath's Marauders Captivating Crew Academy Manufactor Mistmeadow Skulk Changeling Outcast Morbid Opportunist Aetherborn Marauder Tenured Inkcaster Impulsive Pilferer Humble Defector Graywater's Fixer Sorcery Council's Judgment Painful Truths Hex Back in Town Seize the Spotlight Mass Mutiny Requisition Raid Feed the Swarm Artifact Idol of Oblivion Bounty Board Lightning Greaves Glittering Stockpile Arcane Signet Trailblazer's Boots Orzhov Signet Sol Ring Rakdos Signet Bandit's Haul Enchantment We Ride at Dawn Discreet Retreat Rain of Riches Life Insurance Shiny Impetus Instant Heliod's Intervention Dead Before Sunrise Deadly Dispute Shoot the Sheriff Boros Charm Curtains' Call Land Fetid Heath Command Beacon Vault of the Archangel Dragonskull Summit Temple of Silence Temple of Malice Exotic Orchard Temple of Triumph Clifftop Retreat Isolated Chapel Caves of Koilos Battlefield Forge Sulfurous Springs Rugged Prairie Desolate Mire Shadowblood Ridge Canyon Slough Smoldering Marsh Blackcleave Cliffs Command Tower Bojuka Bog Path of Ancestry Rogue's Passage Demolition Field Tainted Peak Sunhome, Fortress of the Legion Nomad Outpost Temple of the False God Bonders' Enclave 2 Plains 4 Swamp 2 Mountain Token Mercenary / Treasure Inkling / Treasure Mercenary / Treasure Rogue / The Monarch Rat / Blood Eldrazi / Clue Assassin / Food Bounty card: Squeakers the Sly Bounty card: Eriana, Wrecking Ball Bounty card: Lyssa, Sterling Collector For more information on this rootin' tootin' Magic: The Gathering set, check out a full rundown of everything you need to know about MTG Outlaws of Thunder Junction

Just add trample to ensure it hits even if blocked
it has earned its pedigree through multiple formats, from Standard right through to Legacy