Romeo and Juliet is the most to blame for the bad choices include evidence

Romeo and Juliet both make impulsive, bad decisions that end with each of them committing suicide.
First, Romeo shows his impulsive nature when he says,

O, she doth teach the torches to burn bright! It seems she hangs upon the cheek of night Like a rich jewel in an Ethiope’s ear; Beauty too rich for use, for earth too dear! So shows a snowy dove trooping with crows, As yonder lady o’er her fellows shows. The measure done, I’ll watch her place of stand, And, touching hers, make blessed my rude hand. Did my heart love till now? forswear it, sight! For I ne’er saw true beauty till this night. (act 1, scene 5)

Here he is proclaiming his love for Juliet, whom he just met—right after wallowing in his sadness over his unrequited love for Rosaline. He changes his mind quickly and doesn't think things through.
Later, Juliet shows her impulsive nature when she talks about marrying Romeo. Even though she knows they are moving too fast, she is caught up in her love, or infatuation, for him.

Three words, dear Romeo, and good night indeed. If that thy bent of love be honourable, Thy purpose marriage, send me word to-morrow, By one that I’ll procure to come to thee, Where and what time thou wilt perform the rite; And all my fortunes at thy foot I’ll lay And follow thee my lord throughout the world. (act 2, scene 2)

Even though it was a decision made for love, getting married so quickly without the support of their families was the first bad decision that both Romeo and Juliet made.
Later, when Romeo thinks Juliet is dead, he says,

And shake the yoke of inauspicious stars From this world-wearied flesh. Eyes, look your last! Arms, take your last embrace! and, lips, O you The doors of breath, seal with a righteous kiss A dateless bargain to engrossing death! Come, bitter conduct, come, unsavoury guide! Thou desperate pilot, now at once run on The dashing rocks thy sea-sick weary bark! Here’s to my love! [Drinks] O true apothecary! Thy drugs are quick. Thus with a kiss I die. (act 5, scene 3)

Again his impulsive and impatient nature drive him to make an awful decision to end his own life. Instead of asking someone to help, asking someone what happened, or finding someone to console him, he impulsively decides he cannot go on living.
When Juliet wakes and realizes that Romeo is dead, she says,

What’s here? a cup, closed in my true love’s hand? Poison, I see, hath been his timeless end: O churl! drunk all, and left no friendly drop To help me after? I will kiss thy lips; Haply some poison yet doth hang on them, To make die with a restorative. (act 5, scene 3)

Here, Juliet also acts impulsively. Similar to Romeo, she doesn't reach out for help. She instead makes a rash decision and tragically ends her own life.