Duplantis, the 15-time world record setter, and Karalis, "the man who would have won it all" if it were not for the Swede's dominance, were the only two left in the competition after the 6.10m mark, as Norway's Sondre Guttormsen needed two attempts to clear 6.00m but failed three times at the next height.
Both athletes were still faultless by that point, with 6.10m only Duplantis' third attempt of the competition, and Karalis' fifth. The Swede then cleared 6.15m with his first try to set a new meeting record, before the Greek stunned the crowd by not only bypassing the height, but clearing 6.20m with his first attempt to set a new national record, adding 3cm to his previous personal best.
Despite winning another European crown earlier this month, a injury-plagued summer has prevented Duplantis from showing his best form, yet he looked back to his best and completely unphased by his rival, as he then cleared 6.25m at the first time of asking.
Clearly feeling confident, Karalis then attempted to set a new world record, but he did not come close to keeping the bar on its 6.32m perch. Duplantis then went for the same height, and despite coming closer than Karalis, he also sent the bar tumbling down.
The Athens man then came close with his second attempt, only to catch the bar on the way down, before Mondo didn't get the required height was his second go, meaning both men had one more chance to break the record in Zurich.
It was a height that proved too much for Karalis, whose third failure finally secured victory for Duplantis, who then made his third and final attempt. Having got plenty of speed on the run up, Mondo got over the bar, only to graze it on the way down, and following a wobble, the bar fell to the mat where the Swede threw it in frustration.
The pole vault world record stays at 6.31m, which Duplantis set at the Mondo Classic in Uppsala in March of this year.