If its somehow gotten bigger than the creature with the ability, it will not get a +1/+1 counter

Acid Web Spider Ademi of the Silkchutes Alenni, Brood Recruiter Alessos and Pras, Acrobats Amazing Spider-Girl Amazing Spider-Man Ancient Spider Aquastrand Spider Arachne, Psionic Weaver Arachnoid Arachnus Spinner Arasta of the Endless Web Arasta of the Endless Web Araa, Heart of the Spider Archweaver Argyr, Tidal Spinner Astonishing Spider-Man Blightwidow Borys, the Spider Rider Brood Weaver Broodspinner Cactarantula Canoptek Spyder Canopy Spider Canyon Crawler Chainweb Aracnir Chizak, Apex Arachnosaur Cirina Bargainspinner Copper Longlegs Cosmic Spider-Man Cren of the Spider Brood Darval, Whose Web Protects Deadly Recluse Diligent Webkeepers Doom Weaver Dragonlair Spider Drider Egrix the Bile Bulwark Ember Weaver Ettercap Ezekiel Sims, Spider-Totem Fateweaver Fizik, Etherium Mechanic Frostweb Spider Funnel-Web Recluse Ghost-Spider Ghost-Spider, Gwen Stacy Giant Spider Giant Trap Door Spider Glint Weaver Gloomwidow Gloria, the Great Armorer Glowstone Recluse Gnottvold Recluse Goliath Spider Grappler Spider Graverobber Spider Gwenom, Remorseless Hatchery Spider Hitchclaw Recluse Hoarding Recluse Iron Spider, Stark Upgrade Ishkanah, Grafwidow Janai and Hoppy, Roofskippers Jungle Weaver Juvenile Gloomwidow Kavaero, Mind-Bitten Kessig Recluse Kivni, Orb Weaver Kraza, the Swarm as One Kroble, Envoy of the Bog Kumonosu, the Watchful

2019: Oko, Thief of Crowns from Throne of Eldraine It's hard to not pick Oko as the most broken card of the year just for its endless Elk memes and that one time that someone won an Eternal Weekend by turning a Black Lotus into an Elk, plus the fact that it was swiftly banned in every format and sort of broke Wizards ' brains when they admitted they didn't actually test the +1 on their opponent's stuff and mostly just Elked their own things, for some reason
In the case of Chain Whirlwind , the effect itself cannot be activated, so it was designated as a specially prohibited card in official competitions