Trump and Kim met in Hanoi, Vietnam for a two-day meeting that ended Thursday. The summit was cut short on the final day after both sides failed to agree on denuclearizing North Korea and lifting economic sanctions on Pyongyang.
"South Korea loses the most from the Hanoi summit ending without agreement," according to Alison Evans, deputy head of Asia Pacific country risk at consultancy IHS Markit.
For Seoul, Thursday's developments dimmed prospects of re-starting inter-Korean projects that have been stalled by sanctions, Evans wrote in a Thursday note. Political support for Moon could also fall further, she added.
"Importantly, Moon's support rating has fallen steadily ... Without progress on North Korea, Moon's domestic agenda becomes his only metric of success for voters, who have already criticised his administration for failing to deliver on economic metrics such as unemployment," she added.