The last tributary of the azygos vein is -
Right superior intercostal vein
Hemi-azygos vein
Right bronchial vein
Accessory azygos vein
Tributaries of Azygos vein

Right superior intercostal vein
Right posterior intercostal veins (5 to 11)
Hemiazygos vein
Accessory hemiazygos vein
Right bronchial vein- last tributary that joins Azygos vein just before its termination.
Esophageal, mediastinal and pericardial veins.