Hey!! As per my knowledge Akula-class submarine is the Biggest Submarine in Indian Navy

General characteristics of this submarine are:

Type: Nuclear-powered attack submarine

Displacement:
-surfaced:
-8,140 tons Akula I and Akula I Improved
-8,450–8,470 tons Akula II and III
-submerged:
-12,770 tons Akula I and Akula I Improved
-13,400–13,800 tons Akula II and III

Length:
-110.3 m (362 ft) for Akula I and Akula I Improved
-113.3 m (372 ft) for Akula II and Akula III

Beam: 13.6 m (45 ft)

Draught: 9.7 m (32 ft)

Propulsion:
-one 190 MW OK-650B/OK-650M pressurized water nuclear reactor
-1 OK-7 steam turbine 43,000 hp (32 MW)
-2 OK-2 Turbogenerators producing 2 MW
-1 seven-bladed propeller
-2 OK-300 retractable electric propulsors for low-speed and quiet maneuvering at 5 knots (9.3 km/h; 5.8 mph)

Speed:
-10 knots (19 km/h; 12 mph) surfaced
-28–35 knots (52–65 km/h; 32–40 mph) submerged

Endurance: 100 days

Test depth:
-480 m (1,570 ft) test depth for Akula I and Akula I Improved
-520 m (1,710 ft) for Akula II and III
-600 m (2,000 ft) maximum operating depth

Complement: 73 for Akula I & Improved, 62 (31 officers) for Akula II & III

Sensors and processing systems:
-MGK-500 or 540 active/passive suite
-Flank arrays
-Pelamida towed array sonar
-MG-70 mine detection sonar

Electronic warfare & decoys:
-Bukhta ESM/ECM
-MG-74 Korund noise simulation decoys (fired from external tubes)
-MT-70 Sonar intercept receiver
-Nikhrom-M IFF

Armament:
-4 × 533 mm torpedo tubes (28 torpedoes) and 4 × 650 mm torpedo tubes (12 torpedoes). (K-152 Nerpa has 8 × 533 mm torpedo tubes) 40 torpedoes total
-1–3 × Igla-M surface-to-air missile launcher fired from sail (surface use only)
-Granat cruise missiles, now Kalibr