Robin and Ted are arguably the central couple of How I Met Your Mother – if nothing else, their meeting is the start of the show (and the introduction of Robin to the gang), and the series ends with them reuniting and giving things another chance in the finale flash-forward. Of course, this ending was so controversial that the series actually came out with an alternate finale, which cut this scene, so it’s clear that no matter how important they were to the show, Ted and Robin were not the best-loved of the HIMYM pairs.

https://screenrant.com/how-i-met-your-mother-ted-robins-relationship-timeline-season-by-season/