What are bunker buster bombs used by Israel that allegedly killed Nasrallah?

Israel's military recently conducted a significant airstrike targeting Hezbollah leader Hassan Nasrallah using U.S.-supplied BLU-109 bombs with JDAM guidance kits. These 2,000-pound bombs, also known as "bunker busters," are designed to penetrate fortified underground structures. The airstrike was captured in a video showing Israeli F-15i jets carrying out the mission, where the bombs were deployed to strike Hezbollah's underground command centre.
This operation was part of Israel’s ongoing efforts to neutralise threats posed by Hezbollah, which is backed by Iran. As per reports, the U.S. has provided Israel with bunker buster bombs since 2005, with over 1,000 bombs included in a $6.5 billion military aid package in 2023. These bombs are equipped with delayed fuses, ensuring detonation only after penetrating the targeted bunkers.
The strike resulted in the death of Hezbollah chief Hassan Nasrullah along with both military and civilian casualties, drawing international attention to the precision of Israel's military operations and the destructive capabilities of these advanced weapons.

Bunker buster bombs, also known as ground-penetration munitions, are specialised weapons designed to destroy heavily fortified structures or underground bunkers. These bombs, weighing between 2,000 and 4,000 pounds, are loaded with explosives and equipped with delayed fuses to ensure they only detonate after reaching their target. They can penetrate up to 30 metres of earth or six metres of reinforced concrete, maximising structural damage through their impact and internal explosion.

The concept of bunker busters originated during World War II, developed by German engineer August Coenders and tested between 1942 and 1943. However, these bombs gained prominence in modern warfare, particularly during the Gulf War, when precision-guided munitions became essential for targeting deeply buried enemy assets.

Guided Bomb Unit 28 (GBU-28): Developed during the Gulf War, this 5,000-pound bomb uses laser-guided technology for precision targeting.
Guided Bomb Unit 37 (GBU-37): A GPS-guided bomb effective in adverse weather, capable of hitting deeply buried targets.
Massive Ordnance Penetrator (GBU-57): The largest bunker buster weighing 30,000 pounds, designed to penetrate up to 200 feet of reinforced concrete.
Bunker busters bombs are equipped with advanced GPS or laser guidance systems for precise targeting, reducing collateral damage. Their strong casings allow the bombs to drill deep into hardened structures before detonating, making them ideal for targeting command centres, weapons depots, and other strategic locations.

While bunker busters bombs are not banned by international law, their use in densely populated areas raises ethical concerns, particularly regarding potential civilian casualties. The Geneva Conventions emphasise avoiding unnecessary harm to civilians, making the deployment of such bombs controversial when used in urban environments.