Who were the 313 companions of the Prophet (s) who participated in the battle of Badr and what was their status compared to others? Are all those companions revered by the Shi'a?
Shi'a respect and revere every sincere Muslim who remained obeying the Prophet (SAWA). The companions who took part in the battle of Badr are fully respected unless they did wrong after that. Haatib ibn Abi Balta'ah participated in Badr battle but later on he betrayed the Prophet and Islam by writing a secret letter to the Mushriks of Makkah informing them about the preparations of the Prophet to attack the Mushriks in Makkah.( Siyar A'lamm al-Nobalaa', page 43)
Qudamah ibn Madh'oon was also in Badr battle but later on he committed major sin of drinking alcohol and was punished for that during the government of Umarvibn al-Khattab. ( Siyar A'laam al-Nubalaa' page 162 and al-Esaabah fi Tamyeez al-Sahabah).
We highly respect every companion who fulfilled his duty in obeying Allah (SWT) and the Prophet (SAWA) and did not change till the end of his life.
'Wassalam.