In the Rig Veda the conflicts are mostly between Gods and anti-Gods like Vritra. But the Rig Veda does hint at conflict between Indra and Vishnu.
उ॒भा जि॑ग्यथु॒र्न परा॑ जयेथे॒ न परा॑ जिग्ये कत॒रश्च॒नैनोः॑ । इन्द्र॑श्च विष्णो॒ यदप॑स्पृधेथां त्रे॒धा स॒हस्रं॒ वि तदै॑रयेथाम् ॥ ६.०६९.०८
6.69.8 (Brererton and Jamison translation)
You both have conquered; you are not conquered. Neither one of these two has been conquered.O Viṣṇu and you Indra, when you two were contending, you broke apart the thousand in three parts.
But head-on conflicts between Gods seem to be recorded only in the Itihasas and Puranas.