He finds that lawyers working with serial plaintiffs will file a bundle of “drive-by” lawsuits at once, slamming businesses with vaguely-worded grievances that leave many companies wondering what they have done wrong.
词汇突破：
plaintiff 原告
Bundle 一系列
drive-by 同谋作案;一个俚语来自电影：侠盗猎车手
grievance 愤怒
vaguely-worded 含糊的措辞
file 提交，发起
businesses 企业，公司
slam 指责
长难句解析：
主干识别： He finds that +宾语从句
其他成分： lawyers will file a bundle of lawsuits at once 宾语从句
Working with serial plaintiffs定语修饰lawyers，
Slamming businesses with vaguely-worded grievances状语
that leave many wondering what they have done wrong定语从句(相当于一个结果状语)
参考译文：他发现律师与连环原告一起合作，一次性提出一系列捆绑案件，用含糊的措辞来指责被告企业，令他们疑惑自己究竟做错了什么。