By Leo Marchandon Feb 12 (Reuters) - Dutch payments processor Adyen's revenue grew more than a fifth in the second half of 2025, but weaker-than-expected transaction ‌volumes and a cautious guidance for 2026 sent its shares falling 15% ‌on Thursday. Its processed transaction volumes rose 19% to 745 billion euros ($885 billion) in the second half of the ​year, missing market forecast of 771 billion euros. Analysts from KBC Securities said in a note that higher fees per transaction partially offset this ...