"World's largest heat pump" is a 🇫🇮 lämpöpumppu (the only Finnish word I know, don't ask)And in the competition for largest heat pumps, it is a bit like the Olympics: with many subcategories (heat source), there are many winners

A 25 MW waste water heat pump in Utrecht
https://www.eneco.nl/en/about-us/what-we-do/sustainable-sources/heat/heat-pump-at-utrecht-sewage-treatment-plant/

The examples are multiplying - as with heat pumps, which use 1 unit of electricity to produce 3-4 units of heat to supply the district heating:
Helsinki is a world leader, with a 500 MW seawater heat pump system under construction:

https://www.bloomberg.com/news/articles/2022-10-18/helsinki-utility-finds-a-surprising-heat-source-icy-seawater

Water works with heat pump in Frederiksberg (don't know the capacity, yearly output is 40 GWh of heat)

https://www.frb-forsyning.dk/om-os/nyheder/byggeriet-af-danmarks-foerste-hoejhusvandvaerk-starter?PID=18090&M=NewsV2&Action=1

Hamburg : 60 MW heat pump (4 x 15 MW) using waste water to heat district heating

https://www.pv-magazine.com/2023/06/01/hamburg-to-deploy-large-scale-heat-pumps-in-wastewater-heat-project/

50 MW heat pump system for Esbjerg using the Wadden Sea as a heat source to heat the district heating system - and with its flexibility in electricity use helps integrate wind power & balance the grid

https://www.man-es.com/discover/esbjerg-heat-pump

Mannheim, (for now) leading in the 'river' heat source category with a 20 MW heat pump

https://www.mvv.de/ueber-uns/unternehmensgruppe/mvv-umwelt/aktuelle-projekte/mvv-flusswaermepumpe

Berlin : 75 MW waste water heat pumps under construction:

https://www.linkedin.com/pulse/heat-pumps-action-berlins-sustainable-future-karim-amin-scqif

Köln / Cologne getting ready for some 'chaleur de cologne' and to take over the lead from Mannheim (from the same river) with the world's largest river heat pump: 150 MW

https://www.rheinenergie.com/de/unternehmen/newsroom/nachrichten/news_71240.html

25 MW heat pump now in operation in Stuttgart

https://www.enbw.com/presse/grosswaermepumpe-liefert-fernwaerme-fuer-10-000-haushalte.html

Kiel using sea water in the Kieler Fjord:

https://www.stadtwerke-kiel.de/privatkunden/nachhaltigkeit-soziales/waermewende-kiel/dekarbonisierung-der-kieler-fernwaerme

"Wrompa" is Poland's largest heat pump: once operational, it will be able to transfer 12.5 MW of heat from wastewater to the district heating system (which is currently 100% coal-based)

https://www.gov.pl/web/climate/wrompa---heat-pump-in-wroclaw

60 MW heat pump for Flensburg’s district heating, using sea water as heat source

https://www.stadtwerke-flensburg.de/foerdepost/presse/grosswaermepunpe-johanson-controls
https://www.ndr.de/nachrichten/schleswig-holstein/Stadtwerke-Flensburg-bestellen-riesige-Meerwasser-Waermepumpe,waermepumpe204.html

Scheduled for operation this year: 60 MW heat pump for Hamburg district heating, using sewage as a heat source

https://www.hamburgwasser.de/umwelt/energiegewinnung/abwasserwaerme

From: @klimareporter
https://mstdn.social/@klimareporter/113837219477713300

Mannheim , which has had a 20 MW heat pump using the Rhine as a heat source for two years, is planning to add two more: one 100 MW unit and another with a capacity of 150 MW. The latter is on a par with the Rhine heat pump under construction in Cologne, but Mannheim leads on total capacity.

https://www.swr.de/swraktuell/baden-wuerttemberg/mannheim/zwei-grosse-flusswaermepumpen-in-mannheim-von-mvv-geplant-100.html