Srimathe Ramanujaya Namaha,
Duryodhana didn’t have any good character at all for Bhishma to see. It was Bhisma’s initial ignorant Prathigya (vow) to his father which is an example of extreme selflessness – and it also serves as a manner of foreshadowing which made him the sacrifice his life for his father’s lust for a young female Sathyavathi. So, his doltish vow with a combination of Amba’s curse to Bhishma masked him from acting against the injustice done to Draupadhi in the sabha, due to which SriKrishna was very very very angry, not only with Bhismha but also with all others in the sabha like Kripacharya etc…..
Bhisma’s Body, Mind, Athma was contaminated initially by consuming food under the Nasthika Duryidhana regime with Dritharastra as the King. He was able to get out of his ignorance only after all his blood were drained in post war while lying in the bed of arrows, that’s when he recited Sri Vishnu Sahasranaamam with clear mind, after which he was deemed ok.
Adiyen (ElayaAlwar) Srnivasa (DhoddayacharyAr) Dasan.