Many companies use negative tactics to undermine their competitors. They spend a lot of time and energy to harm their rivals, who are often much smaller in size.
Some of the negative tactics used (and personally experienced)
1. Intercepting emails.
2. Hacking websites
3. Launching DDOS attacks
4. Spreading false and malicious stories
5. Using fake credit cards and stolen accounts for sign ups.
6. Harassing customers on phone.