Most Badass hindu God which I would love to mention about is Lord Krishna. Starting right from his childhood. As a kid growing up in Brindavan, he sent a whole lot of  Asuras sent by Kamsa to their death. Then he dances on the hood of  the mighty serpent Kaliya, forcing him to leave the Yamuna.

And if that is not enough, he advises the villagers to worship Govardhana mountain, since that is the real life giver, instead of Indra.  And when Indra unleashes his anger, sending a huge thunderstorm, he lifts up the entire mountain on his finger, protecting all the villagers, making Indra eat humble pie there.

When he goes to meet Kamsa, his maternal uncle who had been trying to kill him from long, he  first gets rid of the wrestlers Chanura and Mushtika, along with brother Balaram. And then throwing down Kamsa from the throne, strangles him to death.

He cleverly gets rid of Shishupal, making him exhuast the “100 mistakes I spare his life”  promise he had given to the latter’s mother. And earlier he had eloped with Rukmini who was betrothed to Shishupal, but  had her heart on Krishna.

He did not lift a single weapon during the Kurukshetra war, yet he managed to outsmart the entire Kaurava army, though he only was Arjun’s charioteer. He knew the weak points of  Bheeshma, Drona, Duryodhan,Karna and smartly used it against them. He was the reason why the Pandavasa managed to win against a vastly larger and superior Kaurava Army.

He Stole clothes of Gopis and asked them to come out of water one by one to get cloths back …

Made sure Bhishma won’t kill the Pandavas by asking Draupati to go to his camp in disguise of a common woman. Bhishma blessed her “deerga sumangali bhava” (long marriage). She then revealed her true identity and demanded that Bhishma cannot kill her 5 husbands (the pandavas) because he cannot break his own blessing. (Simply brilliant ahh?)

Engineered killing of Drona. He knew no one can kill Drona as long as he holds a weapon, and only way to make him drop it is to emotionally break him down by telling that his son died. There is no way anyone would disbelieve Yudhishtira as he is the “king of dharma”. So Krishna named an elephant as “ashwtthama” (name of Drona’s son) and asked Bhima to kill it, and then asked Yudhishthira to shout “Ashwatthama, the elephant is dead..” but “the elephant” part of the sentence in a low voice. So Drona, who was at a distance could hear only “Ashwatthama is dead“. As expected, Drona dropped weapons heart broken and Pandavas killed him with ease. (So technically, Yudhishthira the “king of dharma” didn’t lie. Hmmm..)

Made sure Bhima could kill Duryodana. Here is the story. When the war was around the corner, Duryodana was once asked by his mother Gandhari to come to her room fully naked. Duryodana didn’t know why but to carry out his mothers order, he decided to do as asked. But Krishna brain washed him to cover at least the private parts (including thigh).

In her room, Gandhari (who blindfolded herself forever after marrying blind Dritarashtra), opened her eyes to see her son for the first time. She transferred all her powers into Duryodana’s visible part of the body, making them as strong as iron. During the final duel, Krishna instructed Bhima to hit Duryodana on thighs to kill him

Engineered killing of Jarasandha: Here is the story from wiki
Bheema did not know how to defeat Jarasandha. Since, Jarasandha was brought to life when the two lifeless halves joined together, conversely, he can be killed only when these his body was torn into two halves and find a way as how these two don’t merge. Krishna took a stick, he broke it into two and threw them in both directions. Bheema got the hint. He tore Jarasandha’s body into two and threw the pieces in two directions. But, these two pieces came together and Jarasandha was able to attack Bheema again. Bheema got tired after several such futile attempts. He again sought the help of Krishna. This time, Lord Krishna took a stick, broke it into two and threw the left piece on right side and the right piece on the left side. Bheema precisely followed the same. Now, he tore Jarasandha’s body into two and threw them in opposite directions. Thus, Jarasandha was killed as the two pieces could not merge into one.

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Saved Bhima fom Dritarashtra’s hug: Yeah literally! Here is the story:
Dritarashtra was blessing Pandavas after war. He hugged them one by one. When it was Bhima’s turn he remembered that Bhima killed most of his 100 sons. He was furious and wanted to kill Bhima. Krishna knew this and pushed a metal statue to blind Dritarashtra instead of Bhima. Dritarashtra crushed that metal statue into powder with his hug (what a sweet embrace)

He took Pandavas away the night Ashwatthama destroyed Pandava camp after they won the war. He knew it was going to happen. Ashwatthama, with KalBhairav entered into his body, burned the Pandava camp into ashes killing every single person.. But Krishna saved just the Pandavas & Draupati.. Why didn’t he save others? No idea! Might be that he wanted to do a balancing act.
Some more stories of Shri Krishna in short:

1. Putana

She disguised herself as an angelic woman and offered Yashoda a brief respite by volunteering to nurse baby Krishna (with her poisonous milk).  Can we say Krishna “sucked the life out of her?”

2. Trinavarta

the Tornado Demon!  Trinavarta is probably the most unique rakshasa-form – ruthlessly sabatoging everything in his path.  He whisked Krishna off his feet…but Krishna blew him (and his pride) away.

3. Bakasura

Bakasura – the Crane Demon – simply got greedy.  Lured by Kamsa’s promises of rich and swanky rewards, Bakasura “tricked” Krishna to come close – only to betray the boy by swallowing him.  Krishna forced his way out of course and put an end to him.

4. Aghasura

This giant Serpent Demon slithered his way to the outskirts of Gokul, opened his mouth wide and had all the kids squealing in delight by thinking they had discovered a brand new “cave.”  They all hopped inside – only to be trapped.  Some versions of the story explain Aghasura to have once been a handsome king who was cursed by a crippled sage for laughing at the poor man’s disability.

5. Dhenukasura

This Donkey Demon was a real pain-in-the-Ass.  Even Mother Earth trembled under Dhenukasura’s stampede.  This was a true joint venture between Balaram and Krishna – with Balaram taking the credit for the final blow.

6. Aristasura

A true bull-y in every sense of the word.  Aristasur the Bull Demon stormed into town and challenged Krishna to a bull fight that all the heavens watched.

7. Vatsasura

Another story of deception:  Vatsasura disguised himself as a Calf, mixed himself into Krishna’s herd and tricked him into a duel.

8. Keshi

This Horse Demon was apparently mourning the loss of so many of his fellow rakshasa friends, so he approached Kamsa to sponsor his battle against Krishna.

Credits:
Ratnakar Sadasyula
Gireesh Puthumana
Image credit to the original Uploader
Short stories credit : Gnaana.com