The circumstances of encountering the boss: Shiva is a boss connected with the side mission concerning ruining her plans of murdering the corrupt police officers. You encounter this character at the very end of this optional mission, after you reach the Wonder Tower - Lobby in the Sheldon Park district.
Start the fight with Shiva by pressing the counter-attack key/button to repel the simultaneous attack from all of the Batman's enemies. In the first part of the fight, Shiva will be helped by the female warriors that you have already dealt with in the mall. As a result, you should know already how to react to their attacks.
To the extent possible, focus on inflicting damage to Shiva, because she will have to lose enough health points for the next phase of the fight to start, instead of eliminating all of her warriors. Also in this case, the key to success is flawless countering the attacks although you do not need to restrict yourself to defensive actions and you can also search for opportunities to deal damage.
After Shiva loses around a half of her health bar, the second phase of the fights will start. This time, Shiva will summon martial artists. In case you have forgotten, you need to keep in mind that they are able of countering some of Batman's attacks. As far as countering is concerned, you need to remember to tap the counter-attack key/button twice to counter the entire sequence.
Also in this phase, you do not need to eliminate all of the Shiva's men, although this can be helpful a bit, while attempting to attack the boss. The Assassin will probably start using the katana so, do not forget about the necessity to hold down the counter-attack key/button. Keep depleting Shiva's health bar and be prepared to tap twice the key/button shown on the screen, towards the end of the fight. This will block the last blow with the sword.