Shishi Hōkōdan

Lit. Lion Roaring-Bullet (獅子咆哮弾): or more simply known as Lion's Roar Blast, is Ryoga's most powerful technique. It was taught to him by an engineer during his wonderings.

Overview
Shishi Hōkōdan was first shown to Ryoga in The Lion's Roar chapter in the manga and From the Depth of Despair, Part I episode in the anime when he was trapped inside a tunnel and unable to use Bakusai Tenketsu to escape because of the soft rocks. The engineer also gave him the scroll that contains the secrets to unlock the perfected version, which Ryoga discovered later. Shishi Hōkōdan was initially developed by civil engineers to help escape from a collapsed tunnel.

By concentrating his depression and anger into his chi, the user is able to unleash a massive blast of energy from his palms. When Ryoga was first taught it, in its imperfect form, the attack was strong enough to either knock out/defeat Ranma in one blow, or require a few shots, depending on his focus. The regular version proved enough to stun the latter noticeably, even when Ryoga was transformed into a small child. He has occasionally been shown to use this to help blow tunnels through solid earth. It should be noted that Shishi Hōkōdan is not limited to Ryoga. Anybody who is able to concentrate his/her depression can form the chi blast, as Ranma was also able to perform it on a few occasions, albeit much weaker.

The technique requires abundance of sadness (as one would be in an event of a cave in) to perform. Alternatively, if one concentrates their confidence they can unleash Mōko Takabisha. Ranma found this strategy more befitting as he could not become depressed enough to perform Shishi Hōkōdan effectively.

Variation
Shin Shishi Hōkōdan (真獅子咆哮弾 - Lit. True Lion Roaring-Bullet): This is the perfected version of Shishi Hōkōdan which creates a pillar of chi blast. The secret to perfecting the technique lay in the use of the chi and the strength of the user's emotions. As chi generated by depression and anger is "heavy," by projecting it into the air, Ryoga creates a massive sphere of chi that has been shown capable of instantly creating an even larger smoking crater,  in what appeared to be a stone foundation,  and later crack the earth around it, reaching the onlookers at what had been considered a safe viewing distance away from the epicentre. The more ki generated and used in this attack, the larger the resultant sphere of destruction; the greatest visual effect was shown when used to utterly vanquish Lime in a single blow. Simply being grazed by the outermost boundary of one of its most powerful strikes was enough to immediately conquer Ranma, despite the latter's attempt to lessen the impact with his weakened Mōko Takabisha. But a full hit from a later (seemingly weaker, given the lack of increased crater size) attempt simply stunned the latter for roughly a minute, quickly followed by a strike with even less impact.

Trivia

 * The Shishi Hōkōdan and its counterpart the Mōko Takabisha are both based on some rather complex Japanese wordplay revolving around the different uses of the term "ki", which can refer to spiritual energy, emotions, ambience and weather conditions. In particular, the Shishi Hōkōdan is a play on the fact that the kanji for "Depression" or "Heavy-Heartedness" is literally a combination of the kanji characters of "ki" and "heavy", resulting in a technique that literally weaponizes heavy-heartedness. Meanwhile, the Shin Shishi Hōkōdan uses a state of utter dejection to allow the heavy ki bomb to phase harmlessly through the user because the Japanese kanji for "Dejection/Dispiritedness" combines the characters "ki" and "slip".
 * In contrast to the Mōko Takabisha, the Shishi Hōkōdan appears multiple times in stories after its debut, making it almost as central a technique to Ryoga as his original Bakusai Tenketsu.