Pig King, Bari and Bamboo Lieutnant are generally said to be the easiest bosses

Barri, Sangoon all u need is knowledge about mechanics, just do c5/c6 few times learn mechanics and those boss rushes will become veery easy. Ofc u will fail in the beggining like everyone just learn mechs.

I plan on doing 5 different C5s until C7 comes out with a new orb slot.  This is ofcourse after I finish doing all C1-C5s for the 1st time rewards.  Maybe i'll do C6s but since the reward is barely better probably not.

If op wants easy c7, i can only say bamboo and bari is very class based. If you are ranged/ mid ranged with big aoe those will be earlly easy.

From personal exp songakshi is most relyable c7 yet, she is somewhat rng based but if you did her enough you know when the rng fcked you up, the rest is easy to learn, BUT you gotta have a dash without body collision for backattacks for easier clears.

I have to warn you tho, c1-6 rewards are just ass and the hussle of getting c7 clears is too high for avg players (my impression) rn.