Cardento was a very successful sire for show jumpers and was especially influential in Sweden before he went to VDL. If you go to that horsetelex pedigree you can sort his offspring by eventing level and see that he has a couple of offspring who have gone at the 3 and 4* level. IIRC he was rejected by the KWPN as a stallion because he was big and slow moving and didn’t look clever enough at the jumps as a 3yr old.
You can see a lot of good information about his Swedish breeding values here:
He probably wouldn’t be my first choice as an eventing sire if I were going out to breed an event horse, but I think if crossed with an elastic, good moving mare with a lot of blood he certainly could (and has) produced event horses. How old is the mare you are considering? How much can you evaluate her? I certainly wouldn’t discount her because of Cardento and I think he is a super stallion, but I also wouldn’t buy her as an eventing prospect purely because of him either and I’d definitely make your decision based on the horse in front of you.