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